Characterization of electrolytic ZrO2/Al2O3 double layer coatings on AISI 440C stainless steel

Electrolytic ZrO2/Al2O3 double layer deposition was conducted on AISI 440C stainless steel in ZrO(NO3)2 and subsequently in Al(NO3)3 aqueous solutions. After drying and annealing, the ZrO2/Al2O3 coated specimens were evaluated by X-ray diffraction analysis, SEM, AES component depth profiling, hardness tests, wear tests, scratch tests, and dynamic polarization tests. Using poly-etheretherketone (PEEK) as a pin, weight loss of the coated specimen was only 1/4 of the uncoated materials. The scratch tests indicated that the adhesion strength of the coating was greater than the yield stress of the metal substrate. Electrochemical polarization tests of the coated specimen and optical photograph or SEM observation revealed 10 times more corrosion resistance than the uncoated in 1 M HCOOH and 3.5% NaCl aqueous solutions.