Effect of Surface Cleanliness on Paintability of Cold-Rolled Steel Sheet

A study was conducted to examine processing factors important to the formation of surface carbon on cold-rolled steel sheet and to investigate the relationship between surface carbon and paint performance in salt-spray tests.

The results show that less surface carbon was produced on coils annealed in an HNX atmosphere than on coils annealed in a DX atmosphere. Electrolytically cleaning sheet prior to annealing resulted in low levels of surface carbon, but the paint performance of this sheet depended on the paint system used. In general, the statistical correlation between salt-spray corrosion ratings and surface-carbon level was relatively strong for sheet annealed in HNX, null for sheet annealed in DX, and sensitive to the paint system used.