Why does the galvanized coating thickness depend on the steel thickness?
The hot-dip galvanized coating is an intermetallic layer of iron and zinc, meaning the zinc and iron react and diffuse into one another to create the galvanized coating. If more iron is available to react with the zinc, a thicker coating can develop. Thicker pieces of steel tend to develop thicker galvanized coatings. Steel chemistry also plays a huge role in zinc coating thickness, with silicon and phosphorus being the primary catalysts of the galvanizing reaction. Steel chemistry and thickness have the biggest effect on the galvanized coating thickness.
Dr. Galv Article – How Metallurgy Affects Galvanizing