Chromating

Chromating, or chromate conversion coating, is a crucial chemical process used to significantly enhance the corrosion resistance of metals, particularly aluminum, magnesium, and most relevantly, zinc-plated or galvanized steel.

Process and Purpose

The process involves dipping the cleaned metal part into a solution containing chromic acid and other specialized chemicals. A thin, protective, gel-like layer composed of chromates (compounds of chromium) spontaneously forms on the metal surface. This layer chemically integrates with the underlying metal.

Chromating serves several functions in the tube and pipe industry:

1. Corrosion Protection: It drastically slows down the rate of zinc corrosion, extending the product's service life.
2. Passivation: It inhibits the formation of white rust—the initial visible form of zinc corrosion—which is vital for maintaining product aesthetics and quality.
3. Adhesion Promoter: The chromate layer acts as an excellent base for subsequent coatings like paints or lacquers, enhancing their adhesion to the galvanized surface.

It is an post-treatment step that solidifies the long-term durability of galvanized products.