Correlation Between Chemical Composition and Adherence of Cr and Co Coatings Deposited by Electric Arc

This paper presents the adhesive strength of FeCr and FeCoCr coatings produced by electric arc thermal spray process on carbon steel plates. Carbon steels are not resistant to corrosion and several methods are used in surface engineering to protect them from aggressive environments such as the marine one. The main objective of this work is the evaluation of the mechanical and metallurgical properties of coatings produced by thermal spray on carbon steel. Five chemical compositions were tested in order to give a large panel of possibility. Coatings were characterized by several methods to result in a screening of performance. The physical properties of coatings were also evaluated by adhesion quantification, using pull-off test, and microhardness measurement. The assessment of microstructural morphology by X-ray diffraction (XRD) and scanning electron microscopy (SEM) was made. The open circuit potential was monitored to evaluate the corrosion tendency. SEM results showed uniformity in the deposited layer and low amount of oxide and porosity. The adhesive strength of FeCoCr alloy coatings was higher than other coating conditions. In the immersion test, all sealed conditions presented high corrosion potential. Semi-quantitative phase calculation was performed by the Rietveld method using XRD. The presence of FeCr, FeCo, and austenite phases was determined. Based on the performed characterizations, the findings suggested that the FeCrCo deposition, with an epoxy sealing, is suitable to be used as an efficient coating of carbon steel in aggressive corrosive environments.