Influence of Nitriding Surface Treatment on Corrosion Characteristics of Ni-free SUS445 Stainless Steel

Abstract

The heat treatments of Ni-free SUS445 stainless steel under nitrogen and argon gas atmospheres were conducted at 1373-1473 K in the present study. The heat-treated samples were characterized by an X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GD-OES), and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The corrosion behavior of the heat-treated samples was evaluated by linear sweep voltammetry (LSV) measurements in a 0.5 mol dm −3 H 2 SO 4 solution. The results revealed that the nitrided stainless steel at 1373 K presents the best corrosion resistance and the AlN, expanded austenite γ N , CrN and Cr 2 N phases appeared based on the XRD results. In contrast, the corrosion resistance of the heat-treated stainless steel under an argon atmosphere was decreased and there was no change in the microstructure.

Effect of chromium content on the corrosion resistance of ferritic stainless steels in sulfuric acid solution

“…4 . For the SUS410, SUS430 and SUS445 stainless steels, although the polarization characteristics for these three specimens are almost similar in shape, the polarization curve of the SUS445 stainless steel shows the same current density as SUS316 stainless steel in the potential region of 0.25–0.6 V vs. SHE [15] . The formation of passive-current peak shifts due to a negative potential by increasing the Cr content, in increasing order; SUS410, SUS430, and SUS445.…”

“…During this holding time, Ar bubbles nucleated on the surface of the sample to remove generated H 2 gas. The potential sweep was conducted from the rest potential to 1.1 V vs. SHE at a scan rate of 0.33 mV s -1 [15] . After the electrochemical measurement, the samples were carefully removed from the cell and cleaned with ethanol.…”

“…SUS430 contains 16–18% Cr and SUS445 contains 22% Cr and 1–2% Mo as the corrosion-resistant elements. The corrosion resistance of SUS445 in an acidic solution is as high as that of SUS316, which is a Ni-containing austenitic stainless steel [15] . However, further improvement of corrosion resistance is needed for the application of these stainless steels in acidic and electrochemical environments, such as fuel cell materials.…”

Studies of Electrocatalyst and Metallic Bipolar Plate for Polymer Electrolyte Fuel Cell

“…We focused on ferritic stainless steel as raw materials and aimed at improving corrosion resistance by nitrogen heat treatment. [10][11][12] The mechanism of its improvement was also investigated.…”