Corrosion Resistance Evaluation of Ni-Al \ YSZ Composite Coatings by An Electrochemical Investigation

Abstract

The composite coating is used to protect carbon steel pipeline from corrosion by Surfacemodification using thermal spraying technique to enhance the corrosion resistance of carbonsteel. In this study the influence of sour hydrocarbon on carbon steel was investigated onsamples taken from Alloys with (API 5L) that used for oil transport pipe lines in North OilCompany in Kirkuk fields and specifically from well (No. K-130) which the oil sample wasbrought as well. The cermets coating (Ni-Al /ZrO2-8Y2O3) were prepared in different mixingratios of Yttria-Stabilized Zirconia (YSZ) with Ni-Al as a self-bonding. Several mixing ratios ofthe binder (Ni-Al) were used to prepare the cermets for thermal spraying coating namely 15%and 50%. In order to study the effect of roughness on the binding of the cermets and hence thecorrosion behavior of the carbon steel another specimen was mechanically abraded to a surfacefinish 800 grit by SiC paper and the cermets mixing ratio (50% YSZ+ 50% Ni-Al) .The thermalspraying gun was located in an angle of 90º in front of the carbon steel specimen and the distancebetween them was 16 cm. The corrosion behavior of the modified surface in comparison withuntreated one was investigated by electrochemical techniques. Two electrochemical techniques(DC and AC techniques) were used. The AC technique was potentiodynamic cyclic polarizationusing Solatron 1287, USA) potentiostat/galvanostate. The EIS measurements for all coatedspecimens show enhancement in the impedance parameters (total impedance |Z|, polarizationresistance (Rp) and the capacitance (C)) comparing to the uncoated one. The cermets thermallysprayed coating show improvement in the corrosion parameters.