Glossary

Mechanical galvanizing is a zinc coating process used to protect steel parts from corrosion by mechanically bonding zinc particles onto the surface. It is commonly used on small steel components such as fasteners, washers, clips, springs, stampings, and other parts that can be processed in bulk.

Unlike electroplating, mechanical galvanizing does not use electrical current to deposit zinc. Unlike hot-dip galvanizing, it does not require dipping the part into molten zinc. Instead, the parts are placed in a rotating barrel or drum with zinc powder, impact media such as glass beads, water, and chemical promoters. As the barrel turns, the glass beads repeatedly strike the parts and cold-weld or mechanically compact the zinc particles onto the steel surface.

The zinc coating provides sacrificial corrosion protection. Zinc is more active than steel, so when the coated part is exposed to moisture, oxygen, or salts, the zinc corrodes first and helps protect the steel underneath. This means mechanical galvanizing can continue protecting small exposed areas even if the coating is scratched or slightly damaged.

Mechanical galvanizing is especially useful for threaded fasteners because it can provide a protective zinc coating with less risk of hydrogen embrittlement than some electroplating processes. Since no electrical current is used to force the coating onto the part, and the process is typically performed at relatively low temperatures, it is often selected for hardened or high-strength fasteners where embrittlement risk must be carefully managed.

The coating is generally more uniform than hot-dip galvanizing on small threaded parts and usually causes less thread buildup. However, it may not provide the same heavy coating thickness as hot-dip galvanizing in severe outdoor environments. The final performance depends on coating thickness, post-treatment, sealing, part geometry, and service conditions.

Mechanical galvanizing should not be confused with mechanical plating, although the two are closely related. Mechanical plating usually refers to thinner mechanically applied metallic coatings, while mechanical galvanizing usually refers to heavier zinc coatings intended for stronger corrosion protection.

AKA: Peen Plating