The influence of preparation of nano-ZrO2/α-Al2O3 gradient coating on the corrosion resistance of 316L stainless steel substrate

Abstract Generally, 316L stainless steel instrumentation tubes working in a humid environment with a large amount of Cl− all the year round have serious corrosion problems, so the stainless steel substrate should be gradiently coated with nano-ZrO2/α-Al2O3 slurry. In this article, the slender 316L stainless steel tube was first ground by magnetorheological fluid and then coated with the slurry, which can not only increase the contact area between the coating and the substrate but also prevent the generation of new substances that have adversely affected the adhesion of the coating. The properties of the samples were characterized and analyzed; the results showed that the substrate ground by magnetorheological fluid is more favorable for bonding with coating under the grinding conditions that the speed of the tube is 210 rpm, magnetic induction intensity is 40.83 mT, and mass ratio of micron and submicron magnetic particles is 2.3. The coating prepared under the above conditions has uniform thickness, flat surface, and can better inhibit the diffusion of Cr of the substrate to its surface. It can be obtained from corrosion resistance analysis that the coating has the highest self-corrosion potential of −0.016 V and the lowest corrosion current density of 0.491 μA/cm2, which indicate that the coating has the strongest corrosion resistance. According to the composition analysis of the coating, the composition of the corroded coating is similar to that of the coating itself, but accompanied by a small amount of Fe, which indirectly indicates that the coating is relatively compact, the coating is well bonded with the substrate, and the coating can protect the substrate; thus, the service life of 316L stainless steel instrumentation tubes is extended.