FinishColorCorrosion ResistanceMaterialCharacteristics
Black NickelBlackVery GoodAll MetalsGenerally used as a matching finish.
CadmiumSilvery GrayVery GoodAll MetalsNot suggested unless absolutely necessary due to toxic chemical concerns
ChromateYellow, Olive Drab, Black, Blue WhiteGoodAll MetalsA dipping process following the zinc/cad process increasing rust resistance.
ChromiumBright Blue WhiteVery GoodAll MetalsBright lustrous finish used when ultimate beauty and appearance are desired.
Colored DyesMost any ColorGoodAll MetalsA dipping process following zinc/cad process for matching or color coding
CopperCopperFairAll MetalsCommon undercoat for nickel or for decorative purposes
Dichromate DipRainbow CastGoodAll MetalsA dipping process following zinc/cad improving resistance to rust
NickelSilverVery GoodAll MetalsHard, stable, often decorative finish
Oxide (Black)Lustre BlackFairFerrous andNon-ferrousChemical immersion that does not add to thickness.  Good wearing qualities.
Passivating Very GoodStainless SteelsA nitric acid dip  to remove foreign materials, brighten, and improve rust resistance
Phos & OilBlackVery GoodAll MetalsCommonly used on clip and clamp spring steel products and other automotive fasteners.
Zinc (Electro)Blue WhiteGoodAll MetalsMost popular finish combining good rust resistance, appearance, and economy

Hydrogen Embrittlement

A real concern

Generally associated with high-strength fasteners, hydrogen embrittled parts can fail suddenly without warning.

Hydrogen is absorbed into (generally) high strength / high alloy products during the pre-plating, acid cleaning or descaling process, and is then trapped in the part during plating. If not properly relieved, the trapped hydrogen migrates to points of high stress concentration (under the head of fasteners, etc.) The pressure creates or extends existing cracks, ultimately causing catastrophic part failure.

Proper baking post plating (defined by ASTM F1941) is critical to help avoid hydrogen embrittlement, but unfortunately it is NOT a guarantee!

Request that your high strength electro-plated parts are tested post plating to help assure application conformance., or, better still, request a plating solution that is mechanically applied and void of hydrogen embrittlement susceptibilities.