Passivity and Semiconducting Behavior of a High Nitrogen Stainless Steel in Acidic NaCl Solution

Yanxin Qiao,Xiang Cai,Jie Cui,Huabing Li

doi:10.1155/2016/6065481

Abstract

The passivity and semiconducting behaviors of a high nitrogen-containing nickel-free stainless steel (HNSS) in 0.05 mol/L H2SO4+ 0.5 mol/L NaCl have been investigated. Results indicated that HNSS offered excellent pitting corrosion resistance in corrosive environments. Three corrosion potential values were observed in potentiodynamic polarization response, indicating the existence of an unstable system. The current transient and Mott-Schottky plots demonstrated that the stability of passive films decreased with the increase of applied potentials. The angle resolved X-ray photoelectron spectrometric results revealed that the primary constituents of passive films formed in 0.05 mol/L H2SO4+ 0.5 mol/L NaCl solution were composed of iron oxides, manganese oxides, Cr2O3, and Cr(OH)3. Meanwhile, it indicated that molybdenum oxides did not exist in the oxide layer, but chloride ions were present in the passive films.

Highlights

Since the first report about the use of nitrogen as an alloying element in 1938, research on the nitrogen-containing stainless steels has been widely carried out [1]
Ningshen et al found that the nitrogen content influenced the semiconducting nature of the passive film and the oxide layers in passive films could be modified by nitrogen additions [16]
No pitting corrosion was detected for all conditions, indicating that high nitrogen-containing nickel-free stainless steel (HNSS) has a relatively superior pitting corrosion resistance

Summary

Introduction

Since the first report about the use of nitrogen as an alloying element in 1938, research on the nitrogen-containing stainless steels has been widely carried out [1]. Nitrogen is a strong austenite stabilizing element and is expected to substitute for relatively expensive element of nickel to make HNSS a resource-saving materials. With these increasing demands, it is necessary to investigate the passive behavior and properties of passive films of the HNSS. In the investigation of passive films on HNSS, Fu et al reported that the ratio between Cr-oxide and Cr-hydroxide increased with the nitrogen concentration [12]. The target is to investigate the passivity behavior and semiconducting properties of surface films formed on a high nitrogen-containing nickel-free stainless steel

Experimental Procedures

Results and Discussion

B A i1 i4

Conclusions