A

A.C.: an electric current which continually reverses its direction of flow in a regular fashion. The vast majority of electricity supply systems use A.C. The other system of electric current transmission is Direct Current (D.C.).

acid: chemical substance whose water solutions exhibit a pH less than 7.

acid descaling: an alternative name for "pickling": a process using acid to dissolve oxide and scale on the work

activation: process of removing last trace of oxide on a metal surface and a thin layer of the metal itself to ensure that the metal surface to be plated is electrochemically active.

adhesion: the attractive force that exists between an electrodeposit and its substrate that can be measured as the force required to separate an electrodeposit and its substrate.

alkaline cleaning: cleaning by means of alkaline solutions.

alternating current: an electric current which continually reverses its direction of flow in a regular fashion. The vast majority of electricity supply systems use A.C. The other system of electric current transmission is Direct Current (D.C.).

ampere: the standard unit of measure of electric current, named after Andre-Marie Ampere, represented by the symbol A. One ampere is the electric current produced in a circuit by one volt acting through a resistance of one ohm.

annealing: a heat treatment process which may be applied to all metals to soften them.

anion: a negatively charged ion.

anode: the fundamental positively-charged electrode (negative pole) in a electroplating tank or bath; opposite to cathode; the electrode in electrolysis (electroplating), at which negative ions are discharged, positive ions are formed, or other oxidizing reactions occur.

anode efficiency: current efficiency of a specified anodic process.

anode film: the layer of solution in contact with the anode that differs in composition from that of the bulk of the solution; the outer layer of the anode itself consisting of oxidation or reaction products of the anode metal.

anodic coating: a protective, decorative, or functional coating, formed by conversion of the surface of a metal in an electrolytic oxidation process.

anodic cleaning: electrolytic cleaning in which the work is the anode. See Also: reverse cleaning.

anodic etching: a form of electrolytic etching where the work being etched is anodic in the electrolytic circuit (in electroplating, the work is the cathode).

anodizing: an electrolytic oxidation process in which the surface of a metal, when anodic, is converted to a coating having desirable protective, decorative, or functional properties.

anolyte: the portion of electrolyte in the vicinity of the anode

antiquing: the process of artificially inducing the natural process of the tarnishing of metals. Depending on the plate type, parts are either darkened with chemical solutions or with specially formulated metal marking inks.

automatic plating machine: a machine for mechanically processing parts through the plating cycle

automatic plating: plating in which the work (cathode) is automatically conveyed through successive cleaning and plating tanks

average current: the comparative value of direct current in a pulse power supply. Calculated as: Duty Cycle x Peak Current

average voltage: the comparative value of a steady voltage in a pulse power supply. Calculated as: Duty Cycle x Peak Voltage

B

barrel plating: plating or cleaning in an which the work is processed in an bulk in an a rotating container.

base metal: a metal that readily oxidizes or dissolves to form ions (the opposite of noble metal)

British thermal unit (BTU): heat required to raise the temperature of 1 lb. of water by 1° F. The BTU/hr. required to raise the temperature of a volume of standard air by a specific number of degrees is calculated by the formula:
Btu/hr = Temp. Rise x CFM x 1.085

bright chrome plating: plating process in which a decorative chromium plate is deposited directly on a nickel plate substrate.

bright dip (non-electrolytic): a solution used to produce a bright surface on a metal.

bright plating: a process that produces an electrodeposit having a high degree of specular reflectance in an the as-plated condition.

brightener: an addition agent that leads to the formation of a bright plate, or that improves the brightness of the deposit.

bronzing: a chemical process generally applied to steel to impart the appearance of bronze (antimony chloride in hydrochloric acid followed by ammonium chloride in dilute acetic acid). The resulting "bronze" film does not have the corrosion resistance of true bronze.

brush plating: a method of plating in an which the plating solution is applied with a pad or brush, within which is an anode and which is moved over the cathode to be plated.

buffer: a compound or mixture that, when contained in an solution, causes the solution to resist change in an pH. Each buffer has a characteristic limited range of pH over which it is effective.

buffing: the smoothing of a surface by means of a rotating flexible wheel to the surface of which fine, abrasive particles are applied in an liquid suspension, paste, or grease stick form

building up: electroplating for the purpose of increasing the dimensions of an article.

burnishing: a form of metal finishing where the surface is treated mechanically so that no appreciable metal is removed but the surface is smoothed.

burnt deposit: a rough, non coherent or otherwise unsatisfactory deposit produced by the application of an excessive current density and usually containing oxides or other inclusions.

bus (bus bar): a rigid conducting section, for carrying current to the anode and cathode bars.

C

casting: a general term covering a production technique where any metal is heated until it is molten and then poured into a mold, allowed to cool and solidify.

catalyst: an element or ion that promotes or assists in a reaction without affecting or changing the element.

cathode: the fundamental negatively-charged electrode (positive pole) in an electroplating tank opposite to anode; the electrode in an electroplating at which positive ions are discharged, negative ions are formed, or other reducing actions occur.

cathode efficiency: the current efficiency of a specified cathodic process.

cathodic cleaning: electrolytic cleaning in an which the work is the cathode. See Also: direct cleaning

cathodic etching: a technique applied to steel workpieces where the workpiece is make the cathode in an electrolytic cell with sulfuric acid as the electrolyte. The anode will generally be lead or stainless steel. When a current is applied, hydrogen will be evolved at the cathode and the surface metal oxide will be reduced. The technique is usually applied immediately prior to electroplating.

cathodic protection: a technique applied to steel where metals anodic to iron (e.g., zinc, aluminum, magnesium) are applied to the surface on the steel workpiece to provide a corrosion resistant surface. The process relies on the fact that where a cell exists between two metals with an electrolyte, one of the metals will corrode and in the process of corroding protect the other metal.

cation: a positively-charged ion.

celsius: a thermometric scale in which water boils at 100° and freezes at 0°, same as centigrade. °C = 0.5556 x (°F – 32°) 5/9 = 0.5556

chelate compound: a compound in an which the metal is contained as an integral part of a ring structure and is not readily ionized.

chelating agent: a compound capable of forming a chelate compound with a metal ion. See Also: chelate compound.

chemical polishing: the improvement in an smoothness of a metal by simple immersion in an a suitable solution. See Also: bright dip

chromium: a lustrous, hard, steel-gray metallic element, resistant to tarnish and corrosion, used in the hardening of alloys and in electro-plating

cleaning: the removal of grease or other foreign material from a surface. See Also: alkaline cleaning, anodic cleaning, reverse cleaning, cathodic cleaning, direct cleaning, diphase cleaning, electrocleaning, solvent cleaning, spray cleaning, ultrasonic cleaning.

cold galvanizing: a term sometimes used to differentiate between electroplating zinc on steel from the hot dipping of steel in molten zinc. It can also refer to a form of painting with specialized paints which result in a film of up to 90 % powdered zinc. The purpose of all these processes is to provide corrosion resistance.

coloring: the production of desired colors on metal surfaces by appropriate chemical or electrolytical action; light buffing of metal surfaces for the purpose of producing a high luster.

color anodizing: a process used only on aluminum and its alloys using dyes to color the anodic film. The anodic process produces a porous film which when fresh will absorb dyes. The anodizing is carried out using the sulfuric acid process. After completion of the anodizing the workpieces are rinsed in cold water and placed in a dye solution. After dyeing, the workpieces are again rinsed in cold water followed by immersion in nearly boiling water. The heat seals the anodic film and the surface remains permanently colored.

complex ion: an ion composed of two or more ions or radicals, both of which are capable of independent existence, for example cuprocyanide (Cu(CN)2)-.

complexing agent: a compound that will combine with metallic ions to form complex ions. See Complex Ion.

composite plate: an electrodeposit consisting of two or more layers of metal deposited successively.

conductance: the capacity of a medium, usually expressed in mhos, for transmitting electric current. The reciprocal of resistance.

conducting salt: a salt added to the solution in an order to increase its conductivity.

conductivity: the current transferred across unit area per unit potential gradient. In an the metric system, K = amperes per sq cm divided by volts per cm. The reciprocal of resistivity.

contact plating: deposition of a metal by the use of an internal source of current by immersion of the work in an solution in an contact with another metal.

conversion coating: a coating produced by chemical or electro-chemical treatment of a metallic surface that provides a superficial layer containing a compound of the metal; for example, chromate coatings on zinc and cadmium or oxide coatings on steel.

copper plating: copper is electrodeposited for conductivity in the printed circuit and electrical industries and for decorative purposes. There are four basic types of copper plating solutions; copper sulfate, copper cyanide, copper pyrophosphate, and copper fluoroborate.

corrosion: gradual solution or oxidation of a metal.

coulomb: the quantity of electricity that is transmitted through an electric circuit in an 1 second when the current in an the circuit is 1 amp. The quantity of electricity that will deposit 0.0011180 g of silver.

coulometer: an electrolytic cell arranged to measure the quantity of electricity by the chemical reaction produced in an accordance with Faraday's law.

covering power: the ability of a plating solution under a set of specified plating conditions to deposit metal on the surfaces of recesses or deep holes.

critical current density: a current density above which a new and sometimes undesirable reaction occurs.

current density (cd): current per unit area; usually expressed in amperes per square foot (asf) or amperes per square decimeter (asd).

current efficiency: the proportion, usually expressed as a percentage, of the current that is effective in an carrying out a specified process in an accordance with Faraday's Law.

D

D.C.: direct current: an electric current which flows in one direction only. Other system of electric current transmission is alternating current (A.C.).

deburring: the removal of burrs, sharp edges or fins by mechanical, chemical, or electrochemical means.

degreasing: the removal of grease and oils from a surface , generally using chlorinated solvents. In the most common form, a liquid solvent is heated in an open topped container. As it boils a hot vapor rises above the liquid. The vapor is held within the container by means of a cooling coil which runs around the inside of the container a short distance below the rim. This cold zone causes the vapor to condense and return to the sump for reboiling continuously distilling itself. See Also: solvent degreasing, vapor degreasing

deionization: the removal of ions from a solution by ion exchange.

depolarization: a decrease in an the polarization of an electrode at a specified current density.

depolarizer: a substance or a means that produces depolarization.

descaling: a process that can be applied to all materials to remove scale. Scale is generally produced during manufacture or storage. Sometimes it is easily seen in the form of rust or millscale, in other instances it is inconspicuous. Various methods are used for this process including blasting, pickling, acid or alkaline sodium hydride treatments, and polishing.

detergent: a surface active agent that possess the ability to clean soiled surfaces.

diaphragm: a porous or permeable membrane separating anode and cathode compartments of an electrolytic cell from each other or from an intermediate compartment.

die-casting: a method of casting in which molten metal is poured, sometimes under pressure, into a mold or die. The die is made of metal and immediately after solidification of the casting the die opens and the casting is ejected.

diffusion coating: an alloy coating produced by applying heat to one or more coatings deposited on a basis metal

diphase cleaning: cleaning by means of a solution that contains a solvent layer and an aqueous layer. Cleaning is effected both by solvent and emulsifying action.

dispersing agent: a substance that increases the stability of a suspension by retarding the flocculation of such particles.

direct cleaning: electrolytic cleaning in which the work is the cathode. See Also: cathodic cleaning

drag-in: the water or solution that adheres to the objects introduced into a bath.

drag-out: the water or solution that adheres to the objects removed from a bath.

ductility: refers to the flexibility of an electroplated deposit; this parameter is critical when bending and forming operations occur after plating.

dummy (or dummy cathode): a cathode in an a plating solution that is not to be made use of after plating. Often used for removal or decomposition of impurities.

duty cycle: in a pulse power supply: On Time / (On Time + Off Time), expressed as %

E

effluent: any gas or liquid emerging from a pipe or similar outlet; usually refers to waste products from chemical or industrial plants as stack gases or liquid mixtures.

electrochemical equivalent: the weight of an element, compound, radical, or ion involved in an a specified electrochemical reaction during the passage of unit quantity of electricity, such as a Faraday, ampere-hour, or coulomb.

electrochemistry: the branch of science and technology which deals with transformations between chemical and electrical energy.

electrocleaning: an electrochemical cleaning process by which a workpiece is first made the cathode in an electrolytic cell. When current is applied, the generation of hydrogen gas from the electrolysis of water at the surface of the workpiece results in a highly efficient scrubbing action. Following initial treatment as a cathode the circuit is reversed so that the workpiece is the anode. Oxygen gas, which is generated at the surface produces a final cleaning action.

electrode: a conductor by means of which electricity enters or leaves a medium. Common examples include an anode or cathode.

electroforming: a specific form of electroplating used where intricate shapes and relatively thin metal deposits are required. Molds of plastic, wax, or sometimes metals are made conductive by application of carbon or metallic powder and are plated by conventional methods. Nickel, copper, or precious metals are generally selected for this form of plating. The mold is generally removed at the completion of the plating process by one of a number of methods depending on the material from which the mold is constructed.

electrogalvanizing: electrodeposition of zinc coatings.

electroless plating: the process of depositing metal from a water-based solution using chemical catalysts for the metal cation reduction process. In this process no external potential (electrical current) is applied.

electrolyte: a conducting medium in an which the flow of current is accompanied by a movement of matter. Most often an aqueous solution of acids, bases, or salts, but includes many other media, such as fused salts, ionized gases, some solids, etc.; a substance that is capable of forming a conducting liquid medium when dissolved or melted.

electrolytic cell: a unit apparatus in an which electrochemical reactions are produced by applying electrical energy, or which supplies electrical energy as a result of chemical reactions and which includes two or more electrodes and one or more electrolytes contained in an a suitable vessel.

electrolytic etch (electro etch): a technique generally applied to steels which attack the surface to produce a clean, oxide free material. It is often used prior to electroplating, especially chromium plating. Since it preferentially attacks edges it will open us small cracks in the surface of the workpiece. Due to this, this process can be used to inspect finishes for flaws.

electroplating: the process of depositing metal from an aqueous solution using an external potential (electrical current) for the metal cation reduction process; usually, the potential applied is DC, but can approach controlled AC with some sophisticated switching devices (pulsed electroplating).

electropolishing: an electrochemical process usually applied to steels, aluminum, and aluminum alloys. This process produces a surface that is bright and highly reflective. In most instances this is used for decorative purposes and is often used in conjunction with some other form of metal finishing such as anodizing, plating, or lacquering.

electrorefining: the process of anodically dissolving a metal from an impure anode and depositing it cathodically in an a purer form.

electrowinning: the production of metals by electrolysis with insoluble anodes in an solutions derived from ores or other materials.

emission: release of pollutants into the air, water, or ground from a source.

emulsion: a suspension of small droplets of one liquid in an another in an which it is insoluble. For the formation of a stable emulsion, an emulsifying agent must usually be present.

emulsifying agent: a substance that increases the stability of an emulsion.

emulsion cleaning: a cleaning technique which acts by emulsifying contaminants. Emulsions are mixtures of two liquids, with one liquid holding the other in a suspension similar to colloidal suspension. The liquids will typically have different polarities and will dissolve different types of materials. One of the liquids is usually water and the other will have non-polar properties. They can therefore be used to dissolve non-polar contaminants like oil and grease from metal surfaces.

etching: etching is sometimes used a surface preparation technique prior to electroplating or for removal of metal such as in the printed circuit industry where material not required on the finished product is removed by a chemical solution. It can also be used as an inspection technique due to its ability to accentuate surface cracks and defects.

exhaust: the gases emitting from a plating or other process.

exhaust volume: the amount of exhaust gas (air, products of combustion and water vapor) leaving the exhaust stack; usually measured in ACFM.

F

fahrenheit: a thermometric scalre in which water boils at 212° and freezes at 32°. °F = (1.8 x °C) + 32°

filter area: quantity of filter media available for collection of contaminants. Expressed in square feet.

filtration: a means of separation where constituents are separated usually by physical methods.

flash (or flash plate): a thin electrodeposit, less than 0.1 mil. See Also: strike.

fluxing: a process used in the heating of metals which may be intended to reduce or eliminate oxidation, confine the products of oxidation, reduce their melting point, and improve fluidity of surface metal layers. Fluxing is generally used in casting, welding, and soldering.

foam blanket: An additive that forms a layer on the surface of electroplating baths that have poor anode/cathode efficiency, to prevent any mist or spray from escaping.

free cyanide: (1) True. - The actual concentration of cyanide radical, or equivalent alkali cyanide, not combined in an complex ions with metals in an solution. (2) Calculated. - The concentration of cyanide, or alkali cyanide, present in an solution in an excess of that calculated as necessary to form a specified complex ion with a metal or metals present in an solution. (3) Analytical free cyanide content of a solution, as determined by a specified analytical method.

frosting: a type of metal finishing where a fine matte finish is produced by using techniques such as acid-etching, blasting, scratch brushing or barreling.
galvanic cell: an electrolytic cell capable of producing electrical energy by electrochemical action.

fume scrubber: a device that uses a liquid spray to remove aerosol and gaseous pollutants from an air stream. The gases are removed either by absorption or chemical reaction. Solid and liquid particulates are removed through contact with the spray. Scrubbers are used for both the measurement and control of pollution.

G

galvanizing: a corrosion protection technique applied only to mild steel, cast iron, and steel alloys in which workpieces are immersed in liquid zinc at 500 degrees Celsius. A zinc/iron alloy is formed at the surface of the workpiece giving it an adherent coating of zinc. Prior to galvanizing, the metal surface must be in a state of moderate cleanliness. This is generally accomplished by light acid pickling or blasting. Galvanized coatings are generally about 0.005 inches thick and can give protection for 10 to 20 years.

gassing: the evolution of gasses from one or more of the electrodes during electrolysis

generator: a device that produces electricity, particularly one that converts mechanical energy into electrical energy.

gilding: a process in which gold is coated on the surface of another base metal. Gold leaf, a layer beaten so thin it is porous to light, is glued or beaten onto the article to be gilded. A similar method applies a fine gold powder mixed with a flammable liquid solvent applied to the article like paint. The solvent is allowed to evaporate or in some cases may be ignited.

gold plating: gold has two specific properties which make it valuable in industrial and commercial uses, it resists oxidation and corrosion to a very high degree and it retains its attractive color. The main advantage of gold plating over other methods of applying gold to surfaces, is that electroplated coatings do not have pores as gilded coatings do. This provides significantly longer lifespans and corrosion resistance.

H

hard chrome: chromium plated for engineering rather than decorative applications. Not necessarily harder than the latter.

heat exchanger: a device such as a coil or radiator that is used to transfer heat between two physically separate fluids.

hood: a shaped inlet designed to capture contaminated air and transport it into the exhaust duct system. Hood types include canopy, side draft, slotted, downdraft, etc.

hot dip coating: see "galvanizing".

hull cell: a trapezoidal box of nonconducting material with electrodes arranged to permit observation of cathodic or anodic effects over a wide range of current densities.

hydrogen embrittlement: embrittlement of a metal or alloy caused by absorption of hydrogen during a pickling, cleaning, or plating process.

hydrophilic: tendency to absorb water

hydrophobic: tendency to repel water

I

immersion cleaning: see soak cleaning

immersion plating: a plating technique similar to electroless plating where a more electropositive metal is dissolved in an electrolyte and is plated onto the surface of a less electronegative metal workpiece. The term immersion plating is used where a deposit is obtained and the plating process then stops. This is distinguished from electroless plating where the deposition of the metal being plated continues to deposit as long as the workpiece remains in the solution.

impeller: another term for fan or pump “wheel”. The rotating portion of the fan or pump designed to increase the energy level of the gas or liquid stream.

indicator (pH): a substance that changes color when the pH of the medium is changed. In the case of most useful indicators, the pH range within which the color changes is narrow.

indium plating: indium is a metal not unlike lead but with friction and corrosion resistance properties that are unique. In fact, the sole purpose of indium plating is improving the friction characteristics of very high-rated bearings.

inert anode: an anode that is insoluble in an the electrolyte under the conditions prevailing in an the electrolysis.

inhibitor: a substance used to reduce the rate of a chemical or electrochemical reaction, commonly corrosion or pickling.

inorganic material: material which will not respond to biological action (sand, cinders, stone). Nonvolatile fraction of solids

ion: a charged portion of matter of atomic or molecular dimensions.

ion exchange: a reversible process by which ions are interchanged between a solid and a liquid with no substantial structural changes in the solid. In practice, most commonly effected by ion exchange resins.

K

kelvin: absolute temperature in the SI system scale.

kHz: kilo-hertz: one thousand hertz, a unit of frequency

L

laminar flow: gas or fluid in parallel layers with some sliding motion between the layers.

lead plating: lead plating does not have many common uses except in the production of electrodes for lead acid batteries. Steel which has been plated with lead is much stronger mechanically and lighter than the same thickness of pure lead. It is also used as a base layer for indium plating. Lead plating solutions contain approximately 100 grams of lead per liter and 40 grams per liter of fluoroboric acid.

leveling: electrodeposited materials tend to be concentrated at sharp corners, peaks, and ridges, due to the fact that current distributed on a surface will tend to concentrate at these irregularities more than in concave surfaces such as recesses. Therefore, when a workpiece with a rough surface is electroplated, the rate of deposition will be faster on convex irregularities resulting in an accentuation of the item's original roughness. To counteract this effect, additives are added to the electrolyte solution to produce a polarization effect concentrated at the peaks and ridges. This polarization effect lowers the current density at the peaks and reduces deposition rates. The net result is to smooth or "level" the surface of the workpiece.

limiting current density: (1) Cathodic: The maximum current density at which satisfactory deposits can be obtained. (2) Anodic: - The maximum current density at which the anode behaves normally, without excessive polarization.

louver: a device comprised of multiple blades, which when mounted in an opening, permits the flow of air but inhibits the entrance of undesirable elements.

M

mA: milli-ampere: one-thousandth of an ampere, a unit of electric current.

matte finish: a dull finish

mechanical plating: the application of an adherent metallic coating by mechanical means involving the compacting of finely divided particles of such metal to form coherent coatings.

membrane: a microporous structure that acts as a highly efficient filter that allows passage of water, but rejects suspended solids and colloidals; depending on membrane type, ions and small molecules might or might not be rejected.
metal alloy: a mixture of metals; a metallic compound.

metal distribution ratio: the ratio of the thicknesses of metal upon two specified areas of a cathode. See Also: throwing power.

metallizing: the application of an electrically conductive metallic layer to the surface of nonconductors; the application of metallic coatings by nonelectrolytic procedures such as spraying of molten metal and deposition from the vapor phase.

metal spraying: the general term is applied to the spraying of one of several metals onto a metal substrate. In general, it is intended to produce three effects. The first, corrosion protection, usually involves the spraying of zinc or aluminum on structural steel components. It is also used on high tensile workpieces, such as those used in the aerospace industry, that can not be electroplated due to hydrogen embrittlement. The second purpose is "hard facing". Materials used in hard facing are tungsten bearing or tungsten carbide materials, cobalt, and nickel with small amounts of chromium, and high manganese chrome materials. These materials provide significant wear resistance. The third application is for salvage purposes. When engineering components are found to exhibit wear while in service, technical and economic considerations may make metal spraying to replace the wear a better alternative to replacement.

The most common method of metal spraying is "flame impingement". The technique uses powdered metal continuously fed into a high velocity flame. The flame atomizes the metal powder into a molten state and the particles are projected by the energy of the flame onto a prepared metal surface. Plasma coating is a similar method which uses radio frequency-induced plasmas at temperatures up to 30,000 degrees Celsius. This methods use is limited to high integrity components where excellent adhesion or sophisticated materials are required.

MHz: mega-hertz: one million (1,000,000) hertz, a unit of frequency.

microinch: one millionth of an inch, 0.000001 in; = 0.001 mil.

micron (µ): one millionth of a meter, 0.001 mm.

microthrowing power: the ability of a plating solution or a specified set of plating conditions to deposit metal in tiny pores or scratches.

mil: one thousandth of an inch, 0.001 in an. = 25.4 µ.

mill scale: the heavy oxide layer formed during hot fabrication or heat treatment of metals.

mist: suspended liquid droplets generally less than 10 microns, generated by condensation from the gaseous to the liquid state, or by breaking up a liquid into a dispersed state, such as by splashing, foaming and atomizing.
molecular weight: the weight of a molecule expressed on a scale in which the carbon isotope weighs exactly 12.0; represents the sum of the weights of all the atoms in a molecule.

motor starter: an electrical control device used to start a motor and to protect the device from current overload condition. A motor starter should be selected to match the operating voltage and horsepower requirements of the motor.

MSDS (material safety data sheet): compilation of data and information on individual hazardous chemicals produced by the manufacturers and importers of that chemical, as required by OSHA’s Hazard Communication Standard, 29 CFR 1910.1200.

N

nickel plating: a very common form of electrolytic deposition that is generally used as an undercoating for subsequent deposits. There are three common solutions for nickel plating: Watt's solution, Sulfuric acid, and electroless plating.

nickelled: coated, covered or plated with nickel.

nitriding: a surface hardening process that is applied only to certain types of steel. This process creates a finish that is the hardest surface attainable using heat treatment processes. The process consists of maintaining a workpiece in a 500 degree Celsius ammonia atmosphere for up to 100 hours. Under these conditions atomic nitrogen combines with surface iron to form iron nitride. The nitrogen slowly diffusesaway from the surface as long as the proper temperature is maintained. The resulting case thickness is therefore dependent on length of heat treatment.

noble metal: a metal that does not readily tend to furnish ions, and therefore does not dissolve readily, nor easily enter into such reactions as oxidations, etc. The opposite of base metal.

O

off time: is the portion of time the pulse power supply has zero current and/or voltage output

ohm: The standard unit of electrical impedance or, in the case of direct current (D.C.) electrical resistance, named after Georg Ohm, represented by the symbol ?. One ohm is a resistance that produces a potential difference of one volt when a current of one ampere is flowing through it.

on time: the portion of time the pulse power supply has current and/or voltage output
organic compound: a compound consisting of carbon, hydrogen and oxygen atoms.

organic matter: the waste from homes or industry of plant or animal origin. Volatile fraction of solids.
organic material: Material that can be broken down by bacteria (fats, meats, plant life).
oxidation: a reaction in an which electrons are removed from a reactant. Sometimes, more specifically the combination of a reactant with oxygen.

oxidizing agent: a compound that causes oxidation, thereby itself becoming reduced.

P

particle: a small, discrete mass of solid or liquid material.

particulate: a particle of solid or liquid matter.

particulate matter: any solid liquid material in the atmosphere.

passivation: the cleaning of stainless steel with nitric acid to remove carbon and other impurities.

passivity: the condition of a metal that retards its normal reaction in an a specified environment and associated with the assumption of a potential more noble than its normal potential.

peak current: the current output of a pulse power supply during the On Time.

peak voltage: is the voltage output of a pulse power supply during the On Time.

peeling: the detachment or partial detachment of an electrodeposited coating from a basis metal or undercoat.

periodic reverse plating: a method of plating in an which the current is reversed periodically. The cycles are usually no longer than a few minutes and may be much less.

permit: an authorization, license or equivalent control document issued by EPA or an approved state agency to implement the requirements of an environmental regulation such as a permit to operate a facility that may generate harmful emissions.

pH: a unit of measure depicting the hydrogen concentration of a solution: Scale 1 to 14. Where 7 is neutral; <7 acidic; >7 basic.

pH adjustment: the act of changing the pH of an aqueous solution by adding acid or caustic.

phosphating: a process that converts the surface of a steel workpiece to iron phosphate usually prior to painting. Before phosphating, the surface of the workpiece must be free of rust and scale. This is usually accomplished with acid pickling, mechanical wire brushing, or blasting. Phosphating is a relatively short process, usually 5 to 20 minutes. Workpieces are generally painted or chromated within 24 hours of treatment since the phosphating provides little corrosion resistance.

pickle: an acid solution used to remove oxides or other compounds from the surface of a metal by chemical or electrochemical action.

pickling: a chemical treatment which removes oxide or scale from the surface of a metal. It most often refers to the use of sulfuric or hydrochloric acid to remove scale formed on mild and low-alloy steel during hot forming operations. Treatment of stainless steel or high nickel alloys is done with hydrofluoric acid, a particularly hazardous material that must be handled with extreme care.

pit: a small depression or cavity produced in a metal surface during electrodeposition, by corrosion, or by corrosion produced during ultrasonic cleaning.

plating range: the current density range over which a satisfactory electroplate can be deposited.

platinum: a metallic silvery-white chemical element with the properties of being hard and relatively inert, and having a very high melting point. Commonly used in jewellery, electrical and laboratory equipment, and industrial catalysts.

polarization: the change in an the potential of an electrode during electrolysis, such that the potential of an anode always becomes more noble and that of a cathode becomes less noble than their respective static potentials. Equal to the difference between the static potential and the dynamic potential.

polishing: the smoothing of a metal surface by means of the action of abrasive particles attached by adhesive to the surface of wheels or endless belts usually driven at a high speed.

polyelectrolytes: synthetic chemicals used as a coagulant aid in waste treatment

potable water: water fit for human consumption

PPM (parts per million): the number of parts of a given pollutant in a million parts of air or water. Units are expressed by weight or volume.

pressure drop: the differential pressure between two points in a system. The resistance to flow between the two points.

pulse-jet cleaning: a cleaning method where a momentary burst of compressed air is introduced through a tube or nozzle to the top cap of a bag. A bubble of air flows down the bag, causing bag walls to collapse behind it. Generic name given to all pulsing collectors.

pulse plating: a method of plating that uses a power source capable of producing square-wave current pulses.

R

R.F.: radio frequency: a frequency in the range within which radio waves may be transmitted, from about 3 kHz to about 3 GHz.

rack plating: a frame for suspending and carrying current to articles during plating and related operations.

random noise: a sound that has an average amplitude and constantly changing frequency.

rectification: the conversion of alternating current (AC) into direct current (DC).

rectifier: a device that converts alternating current (AC) into direct current (DC) by the inversion of the suppression of alternate half-waves of the alternating current.

reducing agent: a compound that causes reduction, thereby itself becoming oxidized.

reduction: a reaction in an which electrons are added to a reactant. More specifically, the addition of hydrogen or the abstraction of oxygen. Such a reaction takes place, for example, at the cathode in an electrolysis.

reflowing: a technique used in the printed circuit board and other industries in which a component is heated in order to melt solder deposits and causing them to flow. It produces a bright, attractive looking material but its main purpose is for quality control. With reflowing, any defect on the substrate will not wet, clearly indicating areas where solder is missing.

reverse cleaning: electrolytic cleaning in which the work is the anode. See Also: anodic cleaning

resist: a material applied to a part of a cathode or plating rack to render the surface nonconductive; a material applied to a part of the surface of an article to prevent reaction of metal from that area during chemical or electrochemical processes.

rheostat: a continuously variable electrical resistor used to regulate and control current. Usually controlled or varied by mechanical means. Sometimes referred to as a variable resistor.

ripple (DC): regular modulations in an the DC output wave of a rectifier unit, or a motor-generator set, originating from the harmonics of the AC input system in an the case of a rectifier, or from the harmonics of the induced voltage of a motor generator set.

robber: an auxiliary cathode so placed as to divert to itself some current from portions of the work which would otherwise receive too high a current density; See Also: thief

rustproofing: a general term that refers to processes applied to steel. It can include painting or galvanizing, but most often refers to phosphating and similar low duty rust preventatives.

S

sacrificial protection: the form of corrosion protection wherein one metal corrodes in preference to another, thereby protecting the latter from corrosion.

saponification: the alkaline hydrolysis of fats whereby a soap is formed; more generally, the hydrolysis of an ester by an alkali with the formation of an alcohol and a salt of the acid portion.

satin finish: a surface finish that behaves as a diffuse reflector and which is lustrous but not mirrorlike.

scale: an adherent oxide coating that is thicker than the superficial film referred to as tarnish.

scrubber: a device that uses a liquid spray to remove aerosol and gaseous pollutants from an air stream. The gases are removed either by absorption or chemical reaction. Solid and liquid particulates are removed through contact with the spray. Scrubbers are used for both the measurement and control of pollution.

sealing (of anodic coating): a process which, by absorption, chemical reaction, or other mechanism, increases the resistance of an anodic costing to staining and corrosion, improves the durability of colors produced in an the coating, or imparts other desirable properties.

shield: a non-conducting medium for altering the current distribution on an anode or cathode.

silver plating: silver, the easiest metal to plate, is deposited for decorative purposes on household and jewelry items. Sometimes it is used by the electrical industry where it is plated over copper to improve corrosion resistance.

slurry: a suspension of solids in water.

soak cleaning: cleaning by immersion without the use of current, usually in an alkaline solution.

solder plating: the term covers deposition of an alloy of 60% tin and 40% lead that is widely used in the electrical and electronics industries. It provides two valuable features, corrosion resistance and "solderability".

solvent cleaning: cleaning by means of organic solvents.

solvent degreasing: degreasing by immersion in an liquid organic solvent.

specific gravity: the ratio of the weight or mass of a given volume of any substance to that of an equal volume of some other substance taken as a standard. The ratio of the density of any gas to the density of dry air at the same temperature and pressure is the specific gravity of the gas. The ratio of the density of any liquid or solution to the density of pure water at the same temperature and pressure is the specific gravity of the liquid or solution.

specific heat: the ratio of the quantity of heat required to raise a certain volume one degree to that required to raise an equal volume of water one degree.

spray cleaning: cleaning my mean of spraying.

spotting out: the delayed appearance of spots and blemishes on plated or finished surfaces.

stalagmometer: an apparatus for determining surface tension. The mass of a drop of a liquid is measured by weighing a known number of drops or by counting the number of drops obtained from a given volume of the liquid.

stray current: current through paths other than the intended circuit, such as through heating coils or the tank.

strike: a thin film of metal to be followed by other coatings; a solution used to deposit a strike; to plate for a short time, usually at a high initial current density. See Also: flash

stripping: a process in which a coating is removed from the basis metal or undercoat

substrate: surface material or electroplate upon which a subsequent electrodeposit or finish is made. See basis metal.

surfactant: a soluble or colloidal substance having the property of affecting markedly the surface energy of solutions even when present in an very low concentration.

surface tension: that property, due to molecular forces, that exists in an the surface film of all liquids and tends to prevent the liquid from spreading.

T

tank voltage: the total voltage between the anode and cathode of a plating bath or electrolytic cell during electrolysis. It is equal to the sum of: (1) the equilibrium reaction potential, (2) the IR drop, and (3) the electrode potentials.

tarnish: the dulling, staining, or discoloration of metals due to superficial corrosion. The film so formed.

tensile strength: the maximum stress a material can withstand before it breaks; expressed in pounds per square inch.

thief: an auxiliary cathode so placed as to divert to itself some current from portions of the work which would otherwise receive too high a current density.

throwing power: the improvement of the coating (usually metal) distribution over the primary current distribution on an electrode (usually cathode) in an a given solution, under specified conditions. The term may also be used for anodic processes for which the definition is analogous.

total cyanide: the total content of cyanide expressed as the radical CN-, or alkali cyanide whether present as simple or complex ions. The sum of both the combined and free cyanide content of a solution.

transference (or transport, or migration): the movement of ions through the electrolyte associated with the passage of the electric current.

Toxic Release Inventory (TRI): a listing of pollutants and emission levels from each major source.

transformer: an electrical device that transfers energy from one circuit to another by magnetic coupling with no moving parts. Transformers provide a change in voltage, current, phase or other electric characteristic during the transfer and hence are used to convert between high and low voltages, to change impedance, and to provide electrical isolation between circuits.

transmitter: a wireless or radio transmitter; the set that transmits or sends a wireless

trees: branched or irregular projections formed on a cathode during electrodeposition especially at edges and other high current density areas.

U

ultrafiltration: the process that uses membranes to achieve separation of various constituents; a typical ultrafiltration membrane allows water, ions, and small molecules to pass through while rejecting large molecules and suspended solids.

ultrasonic cleaning: cleaning by any chemical means aided by ultrasonic energy; ultrasound used in the cleaning of metal and optical parts by virtue of its vibration rates. Large acoustic forces break off particles and contaminants from surfaces.

vacuum deposition: a process in which certain pure metals are deposited on a substrate. The technique relies on the fact that, in a vacuum, pure metals can be vaporized at a low temperature in a closed container. The metal vapor will condense evenly on all surfaces to produce a metallic coating. Aluminum is the most successfully deposited material, producing a highly reflective finish.

vapor degreasing: degreasing by solvent vapors condensing on the parts being cleaned.

volt: the standard unit of potential difference or electromotive force, named after Alessandro Volta. One volt is the potential difference across a conductor when a current of one ampere dissipates one watt of power.

W

water break: the appearance of a discontinuous film of water on a surface signifying nonuniform wetting and usually associated with a surface contamination.

watt: a unit of power. In electrical terms, the product of voltage and amperage. 746 watts are equal to one horsepower.

wetting agent: a substance that reduces the surface tension of a liquid, thereby causing it to spread more readily on a solid surface.

whiskers: metallic filamentary growths, often microscopic, sometimes formed during electrodeposition and sometimes spontaneously during storage or service, after finishing.

work (in plating): the part that is being electroplated or electroless plated.

workpiece (in plating): the part that is being electroplated or electroless plated.

yield strength: maximum stress to which a ductile material can be subjected before it physically distorts.

Z

zinc phosphating: a process applied to freshly zinc plated workpieces that are immersed in a zinc phosphate solution acidified with phosphoric acid. The zinc surface deposit is converted to zinc phosphate. The workpieces are then immersed in a dilute chromic acid solution to seal the zinc phosphate deposits and prevent rust formation of unsightly zinc oxide.

zinc plating: a common form of plating used to provide corrosion resistance for steels.

zincate treatment: a treatment necessary for aluminum and its alloys before electroplating. After cleaning, etching in chromic or phosphuric acid to remove oxide and dipping in nitric acid to activate the surface, workpieces are immersed in a sodium zincate solution. Metallic zinc is deposited on the surface of the workpiece. It is then rinsed and immediately brought the final plating operation.