Glossary of Plating Terms

Terms in the Metal Plating and Finishing Industry


Abrasive Blasting - A process for cleaning or finishing by a means of an abrasive directed at the work piece at differing pressures & velocities. Grits range from extremely fine (plastic media) to very coarse (aluminum oxide). A grit is available for almost any application.

Activation - Elimination of a passive condition on a surface

Adhesion - The attractive force that exists between an electro-deposit and its substrate that can be measured as the force required to separate an electro-deposit from its substrate.

Anodic Coating - A protective, decorative, or functional coating, formed by conversion of the surface of a metal in an electrolytic oxidation process.

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.


Basis Metal (or Material) - Material upon which coatings are deposited. 

Bright Dip (Non electrolytic) - A solution used to produce a bright surface on a metal. 

Bright Plating - A process that produces an electro-deposit having a high degree of specular reflectance in the as-plated condition. 

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. 


CASS testing - the Copper-Accelerated Acetic Acid Salt Spray test is the same as the Neutral Salt Spray (NSS) test, except it is accelerated, with typical time cycles being 8 and 24 hours.

Copper - is an excellent undercoat in the plating process. Copper provides good conductivity and forms an excellent protective barrier between the base metal and the plate. There are three ways to plate copper: A copper strike promotes good adhesion and will activate the surface; a cyanide copper provides protection and good coverage, particular in pieces that have complex geometric shapes, and also promotes good adhesion; an acid copper levels the surface well, gives a very bright deposit, and can be used as a substitute for nickel.

Chromate - is a conversion coating that provides moderate protection against tarnishing, primarily to enhance shelf-life.

Chemical Polishing - The improvement in the smoothness of a metal part by simple immersion in a suitable solution. See Bright Dip (Non-electrolytic). 

Cleaning - The removal of grease or other foreign material from a surface. 

 Alkaline Cleaning - .cleaning by means of alkaline solutions. 

 Anodic or Reverse Cleaning - Electrolytic cleaning in which the work is the anode. 

 Cathodic or Direct Cleaning - Electrolytic cleaning in which the work is the cathode. 

 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. 

 Direct Current Cleaning .-See Cathodic or Direct Cleaning

 Electrolytic Cleaning.-Alkaline cleaning in which a current is passed through the solution, the work being one of the electrodes. 

 Immersion – see Soak Cleaning

 Reverse Current Cleaning – See Anodic or Reverse Cleaning

 Soak Cleaning- Cleaning by immersion without the use of current, usually in an alkaline solution. 

 Solvent Cleaning - Cleaning by means of organic solvents. 

 Spray Cleaning - Cleaning by means of spraying. 

 Ultrasonic Cleaning - Cleaning by any chemical means aided by ultrasonic energy. 

Conversion Coating - A coating produced by chemical reaction that produces a superficial layer containing a compound of the metal, for example chromate coatings on zinc and cadmium, oxide coating on steel. 

Corrosion - (1) Gradual solution or oxidation of a metal. (2) Solution of anode metal by the electrochemical action in the plating cell. 


De-burring - The removal of burrs, sharp edges or fins by mechanical, chemical, or electrochemical means. 

Dye penetrant inspection (DPI), also called liquid penetrant inspection (LPI) - a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). LPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.


Electro-galvanizing. – Electro-deposition of zinc coatings. 

Electroless Plating. - Deposition of a metallic coating by a controlled chemical reduction that is catalyzed by the metal or alloy being deposited.  

Electroplating - The electro-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. 

Electro-polishing - The improvement in the surface finish of a metal effected by making it anodic in an appropriate solution. 

Etch. (v) - To dissolve a part of the surface of a metal. 


Galvanizing - Application of a coating of zinc. 


Hard Chromium - Chromium plated for engineering rather than decorative applications. Not necessarily harder than the latter. 

Hydrogen Embrittlement - Embrittlement of a metal or alloy caused by absorption of hydrogen during a pickling, cleaning, or plating process.


Leveling Action - The ability of a plating solution to produce a surface smoother than that of the substrate. 


Mat Finish (Matte Finish) - A dull finish. 

Mil. - One thousandth of an inch, 0.001 in. = 25.4 µ. 


Neutral Salt Spray test (NSS) - the purpose of the NSS is to observe corrosion of the pre-plate and/or breakdown or lifting of the top coat. The test takes place in a chamber for either 100 hours (standard MIL spec.) or 336 hours (G.M. exterior spec).

Nickel - is usually the layer between copper and a precious metal finish. Nickel protects metallic objects from corrosion and promotes excellent leveling. A bright nickel gives high brightness to the final finish, and a Watts nickel produces a dull matte finish.


Oxidation - A reaction in which electrons are removed from a reactant. Sometimes, more specifically, the combination of a reactant with oxygen. 


Pickle - An acid solution used to remove oxides or other compounds from the surface of a metal by chemical or electrochemical action. 

Pickling - The removal of oxides or other compounds from a metal surface by means of a pickle. 

Pit - A small depression or cavity produced in a metal surface during electro-deposition or by corrosion. 

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. 


Rack, Plating. - A frame for suspending and carrying current to articles during plating and related operations. 


Sacrificial Protection - A form of corrosion protection, wherein one metal corrodes in preference to another, thereby protecting the latter from corrosion. 

Sand Blasting - Abrasive blasting with sand. 

Satin Finish - A surface finish that behaves as a diffuse reflector and which is lustrous but not mirror-like. 

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 colors produced in the coating, or imparts other desirable properties. 

Strike: (1) (n). - A thin film of metal to be followed by other coatings. (2) (n). - A solution used to deposit a strike. (3) (v). - To plate for a short time, usually at a high initial current density. 

Stripn. - A process or solution used for the removal of a coating from a basis metal or an undercoat 

Substrate –See Basis Metal (or Material) 


Tarnish – (v) The dulling, staining, or discoloration of metals due to superficial corrosion. (n) The film so formed. 


Water Break - The appearance of a discontinuous film of water on a surface signifying non-uniform wetting and usually associated with a surface contamination. 

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 electro-deposition and sometimes spontaneously during storage or service, after finishing.  


X-ray fluorescence - is a non-destructive test to determine the thickness of various layers of metal on a part. Common elements measured are: copper, nickel, gold, silver, palladium and rhodium.