Feasibility of ceramic coating to guard stainless steels against intergranular corrosion

Abstract

The aim of this study is to examine the corrosion behaviour of yttria stabilised zirconia (YSZ) coated 304LN stainless steel, with or without bond coat, in order to assess the potential of the coatings to protect stainless steels against intergranular corrosion (IGC). The coatings have been prepared by plasma spraying technique, and their effectiveness in providing corrosion resistance has been examined by carrying out double loop electrochemical potentiokinetic reactivation test, anodic polarisation studies and boiling nitric acid tests. Characterisations of the steel, the coating and the interfaces, supplement the primary corrosion tests. The effectiveness of the coatings has been mainly assessed using the nature of spalling of the coated material subjected to boiling nitric acid tests, and the results have been discussed using the porosity in the coatings and their nature of the interfaces. It can be inferred from the obtained results that the developed plasma sprayed YSZ coatings, with or without bond coat, are unable to act as protective environmental barrier to prevent IGC of the stainless steel substrate primarily due to inappropriate plasma spray processing which leads to considerable amount of interconnected porosity. However, these results provide some interesting guidelines to develop corrosion resistant ceramic coatings.

Effects of sealing on corrosion behaviour of plasma-sprayed Cr2O3–8TiO2 coating

“…1,2 Owing to their lamellar structure and rapid solidification, plasma-sprayed ceramic coatings contain certain amounts of holes, pores and microcracks, which leave paths for electrolytes from the outer surface to penetrate into the substrate, leading to local galvanic attacks and pitting corrosion of the base materials. [10][11][12][13] These structural defects not only decrease the corrosion resistance of the coating-substrate system, but also worsen the mechanical properties and consequently reduce the wear resistance. [14][15][16] Therefore, it is necessary to close the connected holes, pores and cracks of plasma-sprayed coatings.…”

A Study on TiO2-CeO2 nanocomposite coatings for corrosion protection of 304LN stainless steel

“…His work on the ceramic coating of yttria-stabilized zirconia was published by Ghosh S and colleagues as part of a research to determine whether or not it is possible to use a ceramic coating to protect stainless steels against intergranular corrosion by use of plasma spray. Ceramic coatings, he hypothesised, would provide a superior level of resistance [21].…”

Effect of current frequency on coating properties formed on aluminised steel by plasma electrolytic oxidation

“…[6][7][8] Coating the surface of steel is an effective way to improve its properties. [9][10][11][12][13][14][15][16] Plasma electrolysis (PE) is a relatively new method for coating steel, which is based on the principles of anodising process. [17][18][19][20] Plasma electrolytic oxidation (PEO), a derivative of PE, can grow an appropriately thick, well adherent and hard ceramic coating on the surface of the metallic substrate and is more economical and eco-friendly in comparison with conventional coating methods.…”