Resources

Platings, Coatings, and Finishes

Plating, Coating or Finish	For Use On	Degree of Corrosion Resistance	Characteristics
Anodizing	Aluminum	Excellent	Acid electrolytic treatment. Frosty-etched appearance. Hard oxide surface gives excellent protection.
Brass (electroplated, lacquered)	Steel, usually	Fair	Brass electroplated which is then lacquered. Recommended only for indoor decorative use.
Bronze (electroplated, lacquered)	Steel, usually	Fair	Has color similar to 80% copper, 20% zinc alloy. Electroplated and then lacquered. Recommended only for indoor decorative use.
Cadmium (electroplated)	Most metals	Excellent	Bright silver-gray, dull gray, or black finish. Particularly effective corrosion protection in marine applications. Used for decorative purposes. High lubricity.
Chromate (clear)	Zinc and cadmium plated parts	Very good to excellent	Clear bright or iridescent chemical conversion coating applied to plated parts to enhance corrosion protection, coloring, and paint bonding.
Chromate (color)	Zinc and cadmium plated parts	Very good to excellent	Olive drab, blue, gold, bronze, etc. Same characteristics as clear chromate.
Chromium (electroplated)	Most metals	Good (improves with copper and nickel undercoats)	Bright, blue-white, lustrous finish. Has relatively hard surface. Used for decorative purposes or to add wear resistance.
Copper (electroplated)	Most metals	Fair	Used for nickel and chromium plate undercoat. Can be blackened and relieved to obtain Antique, Statuary, and Venetian finishes.
Copper, brass, bronze, miscellaneous finishes	Most metals	Very good indoor	Decorative finishes. Applied to copper, brass, and bronze plated parts to match colors. Color and tone vary from black to almost the original color. Finish names are: Antique, Black Oxide, Statuary, Old English, Venetian, Copper Oxidized.
Dichromate	Zinc and cadmium plated parts	Very good to excellent	Yellow, brown, green or iridescent colored coating same as clear chromate.
Lacquering (clear or color-matched)	All metals	Improves corrosion resistance. Some types designed for humid or other severe applications.	Used for decorative finishes. Clear or colored to match mating color or luster.
Lead-tin	Steel, usually	Fair to good	Silver-gray color. Applied by hot-dip method. Helps lubricity.
Nickel (bright)	Most metals	Excellent indoors. Good outdoors if thickness at least 0.0005 inch.	Electroplated, silver-colored finish. Used for appliances, hardware, etc.
Nickel (dull)	Most metals	Excellent indoors. Good outdoors if thickness at least 0.0005 inch.	Whitish cast. Can be obtained by mechanical surface finishing or a special plating bath.
Passivating	Stainless steel	Excellent	Chemical treatment. Removes iron particles and produces a passive surface.
Phosphate (color coating)	Steel	Superior to regular phosphate and oiled surfaces	Chemically produced color coating. Available in blue, green, red, purple, etc.
Phosphate (zinc or manganese)	Steel	Good	Black in color. Added protection when oiled with a non-drying petroleum oil containing corrosion inhibitors. Good lubricity.
Rust inhibitors	All metals	Varies with type	Oils, greases, etc. Vary in color and film thickness. Usually applied to black oxide finishes. Used to protect parts in transit and temporary storage.
Silver (electroplated)	All metals	Excellent	Decorative, expensive, excellent electrical conductor.
Tin (electroplated)	All metals	Excellent	Silver-gray color. Excellent corrosion protection for parts in contact with food.
Tin (hot-dip)	All metals	Excellent	Same as electroplated but thickness is harder to control.
Zinc (electroplated)	All metals	Very good	Blue to blue-white gray color.
Zinc (hot-dip)	All metals	Very good	Gives maximum corrosion protection. Dull grayish color. Necessitates thread size adjustments to permit assemblability.
Zinc (mechanically deposited)	Steel	Very good	Dull gray, smooth finish. Corrosion protection depends on coating thickness. Good coverage in recesses and thread roots.