Glossary

Dacromet coating is a type of water-based, inorganic protective coating widely used to prevent corrosion on metal parts, especially fasteners such as bolts, nuts, and washers. It is a thin, silvery-gray coating made primarily of zinc and aluminum flakes dispersed in a chromium oxide binder. When applied and baked onto a metal surface, these overlapping flakes form a dense, plate-like barrier that shields the substrate from oxygen, moisture, and corrosive agents.

The coating works in two main ways. First, it provides a barrier effect, where the tightly packed zinc and aluminum flakes physically block corrosive substances from reaching the base metal. Second, it provides cathodic protection, since the zinc in the coating is more electrochemically active than steel and sacrifices itself to protect the underlying substrate. Unlike traditional paints, which rely solely on surface sealing, Dacromet combines both sacrificial and barrier mechanisms, making it highly effective in aggressive environments.

One of its major advantages is that it offers excellent corrosion resistance while applying a very thin film, typically only 4–8 microns thick. This allows fasteners to maintain their dimensions and thread tolerances without the buildup seen in hot-dip galvanizing. It also resists hydrogen embrittlement, which is a risk in electroplated coatings, making it suitable for high-strength bolts and critical structural fasteners. Additionally, Dacromet coatings can withstand high temperatures and provide uniform coverage even on complex geometries, including recessed areas and threads.

Dacromet has been widely adopted in the automotive, construction, and industrial sectors for applications requiring long-term corrosion resistance, such as brake components, chassis fasteners, wind turbines, and outdoor structural steel. However, because it contains hexavalent chromium, environmental and health regulations have led to restrictions and the development of alternatives like Geomet coatings, which offer similar performance without the use of toxic chromium compounds.