How much weight is gained from hot-dip galvanizing bolts?
According to the American Galvanizers Association (AGA) the weight of an item on average will increase about 3.5% from the zinc added during the galvanizing process. However, the AGA goes on to say, “…that figure can vary greatly based on numerous factors. The fabrication’s shape, size, and steel chemistry all play a major role, and other factors like the black weight, the different types of steel that get welded together, and the galvanizing bath chemistry can also have an effect.”
When considering galvanized fasteners this percentage is often lower. For example, the actual increase in the weight of a galvanized 1″ x 10″ A307 hex bolt compared to a plain hex bolt is approximately 0.26%. The zinc thickness requirement for hot-dip galvanizing threaded fasteners is covered by ASTM F2329. This specification states the average minimum coating thickness at 1.7 mils (.0017 in.). Overall the weight increase of fasteners due to zinc from galvanizing is fairly minimal.