Corrosion behavior of chromium conversion coated AZ91C magnesium alloy in sodium borate and sodium chlorid aqueous solutions

الملخص EN

A chromium containing film was deposited on the surface of the investigated AZ91C magnesium alloy by chemical conversion process.

The microstructure and surface morphology of the as- received and coated alloys were initially characterized by optical microscope.

The corrosion behavior of AZ91C before and after coating was studied through weight loss technique by immersion in 3.5% NaCl and borate solutions at various concentrations and pH values.

Surface corrosion products and passivation films were analyzed by X-ray diffraction.

The obtained results showed that AZ91C coated with chromium conversion coating exhibits enhanced corrosion resistance, furthermore X-ray diffraction revealed that corrosion damage was mainly caused by formation of crystalline phase Mg(OH)2.

The addition of borate with different concentration enhanced the protection with efficiency of 86% recorded at 0.2N sodium borate concentration and 3.5% NaCl.