Electrochemical and AFM/SEM studies of Ni-Cr electroplated and sol-gel coated samples

Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to study the surface characteristics and corrosion mechanisms of Ni/Cr electrocoats and Al2O3 sol-gel coats before and after accelerated corrosion tests in a 0.5% NaCl solution at 18°G The results of electrochemical tests show that the corrosion resistance of substrates has been much improved by the application of both coats, and the Al2O 3 coated sample exhibits the better anti-corrosion performance. Surface morphology observations revealed the presence of highly homogeneous and adherent films formed on the metal substrate during the sol-gel process. These films act as a barrier to prevent the substrate from corrosion in the aggressive environment. This sol-gel coating is therefore seen as a promising replacement for that of Cr6+ electroplating.