Corrosion and nitrate marks on the surface of hot-rolled aluminum plates

Corrosion, the surface of the aluminum sheet contacts the surrounding medium. Chemical or electrochemical reactions occur. The metal surface loses its luster, causing surface tissue damage. The corrosion is in the form of dots or flakes, usually white, and in severe cases, powder is produced. This corrosion reduces the corrosion resistance and comprehensive performance of the aluminum sheet.

Copper diffusion, during heat treatment, the copper atoms in the aluminum sheet substrate metal diffuse into the cell aluminum layer to form yellow-brown spots, which are harmful to corrosion resistance.

Nitrate traces, during salt bath quenching, nitrates remain on the surface of the aluminum sheet, showing irregular white patches, which reduces corrosion resistance in severe cases.