Zinc plating is a widely used coating for the corrosion protection of steel. It is used on stampings, fasteners, and automotive components, providing an excellent base for painting. Zinc is usually provided in a chromated condition, which ranges from blue bright, clear to yellow iridescent, to black. Corrosion resistance is good with the yellow chromates reaching 96 hours neutral salt spray to white corrosion. The new generation of clear, trivalent chromates perform equally as well. Older formulations of clear chromates can be expected to reach 12 hours of salt spray resistance before white corrosion. Red rust remains a function of thickness.
High strength steel (tensile strength greater than 1700 MPa) shall not be electroplated. Stress relief: Steel parts with ultimate tensile strength 1000 MPa and above that have been machined, ground, cold formed, or cold straightened, can be stress relieved at a minimum of 375F for three hours or more before cleaning and plating.
Hydrogen embrittlement relief: All electroplated parts 1200 MPa or higher shall be baked at 375F for three hours or more within four hours after electroplating.