Abstract
The objective of this study is to investigate the effect of long-term aging on electrochemical corrosion characteristics of austenitic AISI 304 steel. AISI 304 steel was subjected to aging treatment for an extended period at 700 °C up to a maximum of 10,000 h. The variation in the microstructure of aged specimens was observed with an optical microscope (OM) and a scanning electron microscope (SEM). The electrochemical polarization test was conducted to obtain the corrosion current density (Icorr) and corrosion potential (Ecorr). The metastable intermetallic M23C6 carbides generated in the vicinity of γ/γ grain boundaries and coarsened with aging time. The δ-ferrite island decomposed into σ-phase and M23C6 carbide with an aging time increase. As the aging time increased, the current density increased, but the corrosion potential of the austenitized specimen exhibited a minimum value of 0.04 μA/cm2. The highest pitting resistance exhibited at the austenitized specimen due to the absence of carbides. Consequently, the corrosion resistance of austenitic AISI 304 steel decreases with long-term aging time. The microstructural analyses well support this result.
Highlights
Austenitic stainless steels are chrome-nickel alloy steels with excellent corrosion resistance, high strength, and good weldability
The objective of this study is to investigate the influence of long-term aging on electrochemical corrosion characteristics of AISI 304 steel
The effect of long-term aging of austenitic 304 steel on electrochemical corrosion characteristics has been investigated at a temperature of 700 ◦ C for up to 10,000 h
Summary
Austenitic stainless steels are chrome-nickel alloy steels with excellent corrosion resistance, high strength, and good weldability This excellent corrosion resistance is due to the chromium content higher than 16% that forms an oxide protective film on the surface. They are widely used as essential materials for vessels and pipes in power plants, chemical industries, medical applications, and structural facilities. Even though these austenitic structural materials have excellent mechanical properties and corrosion resistance, they become deteriorated and degraded due to high temperature, high pressure, and long-term use [1,2,3]. The mechanism of sensitization of stainless steel is about Cr depletion due to the generation of metastable intermetallic precipitation, which makes the Cr amount at the grain boundary fall below
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