Corrosion behaviour of Al-Cr-Mo coatings on type 316L SS using DC magnetron sputtering

In the present study, Al-44Cr-11Mo amorphous coating was developed on type 316L SS using reactive balanced DC magnetron sputtering technique in order to increase the corrosion resistance of stainless steel. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods were used to characterize the Al-44Cr-.11Mo coated type 316L SS. XRD showed that Al-44Cr-11Mo was an amorphous structure. SEM images (cross section) showed that the coating thickness to be around 5 μm, Electrochemical tests were carried out in aerated 3.5 wt.% NaCI at 298K. Potentiodynamic polarization test results indicated that the current density of the Al-44Cr-11Mo coated specimen was around 2x10^-7 A.cm^-2 which is significantly lower than 5x10^-6 A.cm^-2 shown by bare type 316L SS. Electrochemical impedance spectroscopy (EIS) study revealed about an order of magnitude raise in polarisation resistance due to the coating. The above studies indicate that Al-44Cr-11Mo system can be used to improve the corrosion resistance of stainless steel. (author)