A study on corrosion behaviors of Ni-Cr-Mo laser coating, 316 stainless steel and X70 steel in simulated solutions with H2S and CO2

摘要

Ni-Cr-Mo coating was prepared by a high power diode laser (HPDL) on X70 steel substrate (X70). In order to widen the application of this coating in oil industry, its surface morphology and corrosion behavior in simulated solutions separately with CO2, H2S as well as a mixed gas of them were studied and compared with those of X70 and 316 stainless steel (316 SS). The results show that X70 and 316 SS display inclusions on the surface before corrosion, while Ni-Cr-Mo coating exhibits a uniform and compact microstructure. Moreover, Ni-Cr-Mo coating has no change in morphology after corrosion, while X70 and 316 SS display severe corrosion and pitting corrosion, respectively. For each simulated solution, Ni-Cr-Mo coating exhibits higher corrosion resistance than X70 and 316 SS. Also, it shows higher polarization resistance than 316 SS and X70 as immersion time lasts, revealing an enhanced and stable anticorrosion performance. Furthermore, the variation trends of electrochemical response was opposite for X70 and 316 SS/Ni-Cr-Mo coating in simulated solutions with CO2, H2S as well as the mixed gas accordingly, which is caused by different corrosion mechanisms. (C) 2016 Elsevier B.V. All rights reserved.