The investigation of effects of carbid forming alloying elements on corrosion behaviour of ferritic stainless steel

ABSTRACT PhD Thesis THE INVESTIGATION OF EFFECTS OF CARBID FORMING ALLOYING ELEMENTS ON CORROSION BEHAVIOUR OF FERRTTIC STAINLESS STEEL Hülya EREN Fırat University Graduate School of Natural and Applied Sciences Department of Metallurgy Education 2005, Page: 134 In this study, corrosion behavior of 0.5, 1.0, 3.0 wt. % amounts niobium added ferritic stainless steel and 1.0 % wt. amounts molybdenum, vanadium and titanium added ferritic stainless steel have been investigated. Samples were obtained with use of casting and forging process. Corrosion experiments were performed by means of AC impedance technique and mass loss methods. Corrosion currents and corrosion rates were calculated from polarization resists obtained AC impedans technique; mass loss obtained with mass loss tests, respectively. 0.1 M H2SO4 and 0.3 M HC1 solutions were used as corrosive environment. Samples were classified as three groups before corrosion tests. The first group samples were expose any heat treatment, i.e. they are under production conditions. The second group of samples were quenched after annealing at 1 100 °C for 1/2 hours although third group samples were annealing at 1 100 °C for 3 hours and then quenched. SEM investigations were performed on surfaces of samples which exposed to aggressive environment for 30 and 360 minutes. As a result; it was observed that heat treatment applied at 1100 °C has increased corrosion resistance of samples. Although they are very close the other, the best result observed from molybdenum containing samples. It was determined that these species steels are more resistant in chloride solutions than sulphuric acid solutions. Keywords: Ferritic stainless steel, corrosion, alloying element, heat treatment X