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Plating Glossary

 
Addition agent
A material added in small quantities to a solution to modify its characteristics or the properties of the deposit obtained from the solution.

Adhesion
The strength of the bond between a coating and its substrate which is measured as the force per unit area required to separate them.

Alkaline blackening (black finishing)
Producing a black oxide coating on steel by immersion in hot alkaline salt solutions.

Alloy deposition
Co-deposition of two or more metals.

Anion
 A negative charged ion.

Anode
 (1) in electrolysis, the electrode at which negative ions are discharged, positive ions are formed, or other oxidizing reactions occur. (2) The object which is intended to perform these functions.

Anode bagging
Some anodes (e.g. Nickel anodes) are put in a cloth bag, before suspension in solution, so that the insoluble particles from the anode are collected in the bag instead of falling into the solution.

Anode corrosion
Dissolution of anode metal by the electrochemical action in the plating cell.

Anode efficiency
Current efficiency of a specified anodic process.

Anode film
(1) The thin layer of a solution which is in contact with the anode and differs in composition from the bulk of the solution. (2) Solid film formed on the anode during operation.

Anode polarization
 See Polarization.

Anodic coating
 (1) A metallic coating on a metal surface, the metal of the coating being less noble compared to that of the basis metal. (Sacrificial coating.) (2) A protective, decorative, or functional coating, formed by conversion of the surface of a metal in an electrolytic oxidation process. (See anodizing.)

A nodizing (anodic oxidation)
An electrolytic oxidation process in which the surface layer of a metal is converted to a coating having protective, decorative, or functional properties.

Autocatalytic plating
 Deposition of a metallic coating by a controlled chemical reduction that is catelyzed by the metal or alloy being deposited.

Banding
Segregation of alloying elements in a metal, seen as parallel bands, in the direction of rolling

Barrel plating
A particular example of barrel processing by which electrodeposits are applied to articles in bulk; in contrast to vat plating in which articles are individually suspended during the electrodeposition process.

Barrel processing
Mechanical, chemical or electrochemical treatment of articles in bulk in a rotating container. Examples : Barrel burnishing, barrel polishing, barrel cleaning.

Base metal
Opposite of noble metal. (Not to be confused with basis metal.) Examples of base metals are aluminium, magnesium, zinc, cadmium, iron, etc.

Basis material (basis metal)
Material upon which coatings are deposited or formed. (Not to be confused with base metal.)

Blackening
Black finishing : Black oxide : See alkaline blackening.

Blasting
 A process in which particles are projected at high velocity against the work piece.

Blueing
The formation of a very thin blue oxide film on steel either by heating in air or by immersion in concentrated oxidizing solutions.

Bright dipping
brief immersion in a solution used to produce a bright surface on a metal

Bright finish
 A finish with a uniform non-directional smooth surface of high specular reflectance.

Bright plating (electrolytic)
 A process that produces an electrodeposit having a high degree of specular reflectance in a as-plated condition.

Bright plating range
The range of current densities within which an electroplating solution produces a bright deposit under a given set of operating conditions.Brightener : An addition agent in an electroplating solution that improves the brightness of an electrodeposit.

Brush plating
A method of electrodeposition in which the electrolyte is applied with a pad or brush in contact with an electrode. The brush or pad is applied to the part to be processed which is given opposite polarity.

Buffer
A substance that, when contained in a solution, counteracts changes in pH.
Each buffer has a characteristic range of pH over which it is effective.


Buffing (Mopping)
The smoothing of a surface by means of a rotating flexible wheel to the surface of which fine, abrasive particles are applied in liquid suspension, paste, or grease stick form.

Burnishing
The smoothing of surfaces by ribbing under pressure, essentially without removal of the surface layer.

Burnt deposit
 A rough unsatisfactory deposit produced by an excessive current density.

Bus bar
A rigid conductor for carrying current, for example, to the anode and cathode bars.

Cathode
In electrolysis, the electrode at which positive ions are discharged, negative ions are formed or other reducing reactions occur.

Cathode efficiency
Current efficiency of a specified cathodic process.

Cathode film
The thin layer of solution which is in contact with the cathode and differs in composition from the bulk of the solution.

Cathode polarization
 See polarization.

Cathodic protection (in electro-deposition)
See sacrificial protection.

Cation
 A positively charged ion.

Chelate compound
 A compound in which the metal atom forms part of a ring-structure and is not readily ionized.

Chelating agent
An organic compound capable of forming a chelate compound with a metal ion. (See chelate compound.)

Chemical polishing
Immersion in a solution to improve the surface smoothness of a metal. (Not to be confused with bright dipping.)

Chromating
forming a conversion coating on a metal surface by means of a solution containing chromium compounds usually in the hexavalent form.

Cleaning:
(a) Alkaline cleaning : Cleaning by means of alkaline solutions.
(b) Anodic (reverse) cleaning : Electrolytic cleaning in which the work piece is the anode.
(c) Cathodic (direct) cleaning : Electrolytic cleaning in which the work piece is the cathode.
(d) Diphase cleaning : Cleaning by means of a liquid system that consists of an organic solvent layer and an aqueous layer. Cleaning is effected both by solvent and emulsifying action.
(e) Direct cleaning : See cathodic cleaning.
(f) Electrolytic cleaning : Cleaning by immersion without the use of current, usually in an alkaline solution.
(k) Solvent degreasing : Cleaning by means of organic solvents.
(l) Spray cleaning : Cleaning by means of spraying with a cleaning solution.
(m) Ultrasonic cleaning : Cleaning by any chemical means aided by ultrasonic vibration.
(n) Vapour degreasing : Degreasing by solvent vapours condensing on the work pieces being cleaned.

Cold swill
 Washing in cold water.

Colouring off
 Light final buffing.

Complexing agent
 A compound that will combine with metallic ions to form complex ions.

Composite electroplate
 See multilayer deposit.

Contact plating
 The deposition of a metal coating upon a basis metal, by immersing the latter in contact with another metal in a solution containing a compound of the metal to be deposited. (Not to be confused with immersion plating.)

Conversion coating
 A coating consisting of a compound of the surface metal produced by chemical or electrochemical treatment.
Example : chromate films on zinc or cadmium or oxide films on steel.
Note: ( Anodizeu coatings on aluminium or magnesium while satisfying these definitions are not normally conversion coatings. )

Covering power
 The ability of an electroplating solution under a given set of conditions to deposit metal on the surfaces of recesses or deep holes. (To be distinguished from throwing power.)
Critical current density (in electroplating): Current density above or below which new and sometimes undesirable reactions occur.

Current density
Current expressed in amperes per unit area.

Current efficiency
The proportion, usually expressed as a percentage, of the current that is effective in carrying out a given process in accordance with Faraday's law.

Deburring
The removal of burrs, sharp edges, or fins by mechanical, chemical or electrochemical means.

Delonization (demineralization)
The removal of ions from a solution by ion exchange.

Depolarization
a decrease i the polarization of an electrode.

Detergent
A surface-active agent that possesses the ability to assist in cleaning soiled surfaces.

Diaphragm (in electroplating)
A porous separator dividing anode and cathode compartments of an electroplating tank from each other or from an intermediate compartment.

Diffusion treatment
Process introduced by diffusion of any metal or non-metal into the surface layer.

Double salt
Two salts that crystallise together in stoichiometric proportions but give the reactions of the ions of the constituent single salts in aqueous solution. Example : rochelle salt.

Drag-in
 The liquid carried into a bath by the objects introduced therein.

Drag-out
The liquid carried out of a bath by the objects removed from there.

Dull Finish
 A finish virtually lacking both diffuse and specular reflectance.

Dummy (or dummy cathode
A cathode used for removal decomposition of impurities from electroplating solutions.

Dyeing (in electroplating)
Imparting a colour by the use of organic dyestuffs.

Electrode
A term denoting anode or cathode.

Electroless plating
Term in use, but not recommended, for autocatelytic plating.

Electrodeposition
The process of depositing a substance upon an electrode by electrolysis. Electrodeposition includes electroplating, electroforming, electrorefining and electrowinning.

Electro forming
Production or reproduction of articles by electrodeposition upon a mandril or former or mould which is as a rule subsequently separated from the deposit.

Electrolyte (colloquial use in electroplating)
 Any conducting solution used for plating or anodizing baths.

Electroplating
The deposition of an adherent metallic coating upon an electrode for the purpose of securing a surface with properties or dimensions different from those of the basis metal.

Electroplating range
The current density range over which a satisfactory electrodeposit can be obtained.

Electropolishing
The smoothening or brigthening of a metal surface by making it anodic in an appropriate solution.

Emulsifying agent Emulsifier
A substance used to produce a stable emulsion.

Etch
To roughen the surface of a metal by selective dissolution.

Etchant
The solution used for etching.

Flash; Flash plate
 A very thin electrodeposit produced in a short time.

Flocculate
To aggregate into larger agglomerates, to increase in size to the point where precipitation occurs, or to facilitate precipitation.

Gassing
 Visible evolution of gases from electrodes during electrolysis.Glass bead blasting : A process whereby small spherical glass beads are propelled against a metallic surface for the purpose of cleaning that surface. It is carried out in either the wet or dry state.

Grinding
 The removal of material b means of rotating rigid wheels containing abrasive.

Grit blasting
 Abrasive blasting with small angular pieces of steel or cast iron

Hull cell
 A trapezoidal box of non-conducting material with electrodes arranged to permit observation of cathode or anodic effects over a wide range of current densities.

Hydrogen embrittlement
Embrittlement of a metal or alloy caused by absorption of atomic hydrogen, for example during a pickling, cleaning or plating process.
Immersion deposit : A metallic deposit produced by a displacement reaction in which one metal displaces another from solution, for example :
Fe + Cu2 Õ Cu + Fe2

Immersion plating
The production of an immersion deposit.

Inert anode
 See insoluble anode.

In hibitor
A substance used to reduce the rate of a specific chemical or electro-chemical reaction, for example, pickling inhibitor.

Insoluble anode
 An anode which does not contribute metal ions to the electrolyte during electrolysis.

Ion exchange (ion exchanger)
A reversible process by which ions are interchanged between a solid and a liquid without substantial structural changes of the solid.

Levelling
The ability of an electroplating solution to produce a surface smoother than that of the substrate.

Liquid honing
See wet blasting

Mandrel
(1) A form used as a cathode in electroforming; a mould or matrix.
(2) Support used in bending tests.
Matt finish (Matt finish) : A uniform finish of a fine texture virtually lacking specular reflectivity.

Matrix
 See mandrel (1).

Metallizing
The application of a metallic layer to the surface of non-metallic materials.

Metal sparying
The application f a metal layer by a process of spraying molten metal from a gun on any basis material.

Milling
 Metal removal using a milling machine.

Mopping
 See buffing.

Multilayer deposit
An electrodeposit consisting of two or more layers of metal of different nature or composition deposited successively.

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. Examples of noble metals are silver, gold, platinum etc.Note : In order to avoid any confusion concerning the sign of electrode potentials, the words noble and base are often preferred because they are unambiguous.

Orange peel
 A finish resembling the dimpled appearance of an orange peel.

Oxidation
A reaction in 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.
pH : The negative logarithm of the hydrogen ion activity (less precisely, concentration) as determined by indicators or electrometric means; used as a measure of the acidity or alkalinity of a solution.

Passivity
The condition of a metal that retards its normal reaction in a specified environment and associated, with the assumption of a potential more noble than its normal potential.

Passivating
Imparting passivity to a metal surface usually by dipping it into a medium (such as preparations containing chromic and / or phosphoric acid) forming a very thin protective surface film.

Peeling
The detachment or partial detachment of an electrodeposited coating form a basis metal or undercoat.

Periodic revers plating
A method of plating in which the current is reversed periodically. The cycles are usually no longer than a few minutes and may be much less.

Phosphating
 (1) Forming a layer of insoluble phosphates on a metal surface. (General usage.) (2) Passivating an electropated article using an agent containing phosphoric acid and / or phosphates. <more>

Pickling
 Removal of oxides or other compounds of the basis metal from a metal surface by chemical or electrochemical action.

Pit
A small depression or cavity produced in a metal surface during electrodeposition or by corrosion.

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

Pore (in a coating)
 Essentially circular micro-discontinuity in the surface extending through to the underlying coating or to the basis metal.

Primary current distribution
 The distribution of the current over the surface of an electrode in the absence of polarization.

Rack; plating rack (jig)
 A frame for suspending and carrying current to articles during electroplating and related operations.

Rectifier
A device that converts alternating current into direct current by virtue of a characteristic permitting appreciable flow of current in only one direction.

Resist
(1) A material applied to a part of a cathode or plating rack to render the surface non-conductive. (2) A material applied to a part of the surface of an article to prevent reaction of metal in that area during chemical or electrochemical processes.

Robber
 See thief.

Sacrificial protection
The form of cathodic corrosion protection wherein one metal corrodes in preference to another, thereby protecting the latter from corrosion (also see anodic coating (1)).

Sand blasting
 Abrasive blasting with sand or related hard material of similar particle size.

Satin finish
 (1) A lustrous finish having a fine directional texture. (2) A fine mat finish which is lustrous without directional texture.

Scale
 An adherent oxide coating that is thicker than the superficial film referred to as tarnish.

Sealing of anodic coating
 A process which, by absorption, chemical reaction, or other mechanism, increases the resistance of an anodic coating to staining and corrosion, improves the durability of colours produced in the coating, or imparts other desirable properties.

Shield
(1) A non-conducting barrier positioned so as to alter the current distribution on an anode or cathode. (2) To alter the current distribution of an anode or cathode by the interposition of a non-conductor.

Shot blasting
A process whereby hard, small, spherical objects (such as metallic shots) are propelled against a metallic surface for the purpose of cleaning or descaling that surface.

Shot peening
 A process whereby hard, small, spherical objects (such as metallic shots) are propelled against a metallic surface for the purpose of cleaning or descaling that surface.

Spotting out
The delayed appearance of spots and blemishes on plated or finished surfaces.

Stopping off
The application of a resist to any part of a cathode, anode, or rack.

Stray current
Current through paths other than intended circuit, such as through heating coils or the tank.Strike : (1) A thin film of electrodeposited metal which improves the deposition of subsequent coatings. (2) A solution specially formulated to obtain this film. (3) To electroplate for a relatively short time either in a bath of a composition or at operating conditions different from those of the subsequent process.

Strip
(1) A process or solution used for the removal of a coating from a basis metal or an undercoat. (2) To remove a coating from the basis metal or undercoat.

Superimposed ac
A form of current in which an alternating current component is superimposed on the direct plating current.

Surface active agent
 A substance that affects markedly the interfacial or surface tension of solutions even when present in very low concentrations.

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

Surface treatment
General term denoting the treatment involving a modification of the surface.
Note : The term is also used in a restrictive sense excluding metallic coatings.

Tank voltage : The total potential difference between the anode and cathode of an electroplating bath or electrolytic cell during electrolysis.

Tarnish, Tarnishing
(1) The dulling, staining, or discolouration of metals due to superficial corrosion. (2) the film so formed.

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

Throwing power
The property of a solutio to obtain an even distribution of the coating on an article of complex shape.

Trees
Branched or irregular projections formed on a cathode during electrodeposition, especially at edges and other high current density areas.

Tripoli
 Friable and dustlike silica used as an abrasive.

Tumbling
 Bulk processing in barrels, either in the presence or absence of abrasives or burnishing shot, for the purpose of improving the surface finish.

Vapour blasting : See wet blasting.

Water break
the appearance of a discontinuous film of water on a surface signifying non-uniform wettability usually caused by a surface contamination.

Wet blasting
 A process for cleaning or finishing by means of a slurry of abrasive in water directed at high velocity against the work pieces.

Wetting agent
 A substance that reduce the surface tension of a liquid, thereby causing it to spread more readily on a solid surface.

Whiskers (in electroplating)
 Metallic filamentary growths, often microscopic, sometimes formed during electrodeposition and sometimes spontaneously during storage or service, after finishing