Investigation of the Effects of Solution Temperature on the Corrosion Behavior of Austenitic Low-Nickel Stainless Steels in Citric Acid using Impedance and Polarization Measurements

Francis M Mulimbayan,Manolo G Mena

doi:10.1051/matecconf/20152702006

Abstract

Stainless steels may be classified according to alloy microstructure – ferritic, austenitic, martensitic, duplex, and precipitation hardening grades. Among these, austenitic grade has the largest contribution to market due to the alloy’s numerous industrial and domestic applications. In this study, the corrosion behavior of low-Nickel stainless steel in citric acid was investigated using potentiodynamic polarization techniques and Electrochemical Impedance Spectroscopy (EIS). The corrosion current density which is directly related to corrosion rate was extracted from the generated anodic polarization curve. Increasing the temperature of the citric acid resulted to increased corrosion current densities indicating higher corrosion rates at initial corrosion condition. EIS was performed to generate Nyquist plots whose shape and size depicts the corrosion mechanism and corrosion resistance of the alloy in citric acid, respectively. All the generated Nyquist plots have depressed semi-circle shapes implying that corrosion process takes place with charge-transfer as the rate-determining step. Based from the extracted values of polarization resistance (Rp), the temperature of the solution has negative correlation with the corrosion resistance of the studied alloy.

Highlights

Stainless steel (SS) is used in numerous industrial and domestic applications worldwide [1]
Between the two austenitic grades – AISI 200 and 300-series, it is the latter alloy which is commonly produced in applications involving food handling and processing, though the use of former alloy has increased considerably due to continuous effort of cutting cost that is achieved by significantly reducing the amount of nickel and using manganese instead
If Ecorr denotes the potential of the alloy at initial corrosion condition, icorr on the other hand, corresponds to the initial corrosion current density

Summary

Introduction

Stainless steel (SS) is used in numerous industrial and domestic applications worldwide [1]. SS may be classified based on its microstructure – ferritic, austenitic, duplex, martensitic, and precipitation hardening grades. The American Iron and Steel Institute (AISI) used three-digit numbering system for SS It consists of a 300-series for chromium-nickel (Cr-Ni) austenitic alloys, a 400-series for high-Cr ferritic and martensitic alloys, a 200-series for austenitic low-Nickel alloys, a 500-series for 4-6% Cr alloys and a 600-series to cover proprietary alloys [6]. Between the two austenitic grades – AISI 200 and 300-series, it is the latter alloy which is commonly produced in applications involving food handling and processing, though the use of former alloy has increased considerably due to continuous effort of cutting cost that is achieved by significantly reducing the amount of nickel and using manganese instead

Methods

Results

Conclusion