Finishes

Features and applications of common 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.