Laboratory Method To Study The Surface Corrosion Of Zro2.5cao + Al2O3 Coatings Applied On Gray Cast Iron Substrate

Abstract

A systematic investigation on surface corrosion of Calcia Stabilised Zirconia, top coat applied to Gray cast iron substrates were examined. To achieve coatings Air plasma spray technique was adopted. A total of nine specimens were prepared for different top coat thickness 100, 200 and 300 µm.The samples were tested for different concentration of 5, 7, & 10% in the aqueous nitric acidic (HNO3 ) medium and continuously examined for weight loss and surface corrosion at an interval of 8, 16 and 24 hours. Surface corrosion tests were conducted with liquid immersion technique to examine the surface oxidation. In this investigation, it has been found that the 100 µm top coat specimens undergoes non uniform corrosion at all the concentration, relatively more compared to 200 and 300 µm coated specimens. Spallation of the top coat realised in case of 100 µm top coat specimens at higher concentration reason attributed to less coat thickness and porosity, facilitating nitric acid to diffuse easily to the underlying bond coat (Fe38Ni10Al) leads to accelerate corrosion of the top coat. All the results of the present investigation were presented in detail