Role of steel and zinc coating thickness in cut edge corrosion of coil coated materials in atmospheric weathering conditions; Part 2: Field data and model

Paint delamination from cut edges of model coil coated hot dip galvanized materials exposed at a marine test site for 5 years increased with steel thickness and decreased with zinc coating thickness. It was larger in sheltered locations than for openly exposed cut edges whereas red rust protection was more efficient on sheltered edges due to higher electric conductivity of deposits. The rate of paint delamination increased or decreased in time depending on the relative amount of zinc ions available for formation of the protective film on steel controlled by the initial steel substrate and zinc coating thicknesses.