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One Minute Mentor: Corrosion Resistance of Carburized 316 Steel

January 08, 2018
Source: ASM International

Electrochemical polarization curves show a 600 to 800 mV increase in pitting potential in treated (900 to 1000 mV) versus nontreated (200 to 300 mV) type 316 in chloride solutions.

Two possible causes for the enhanced corrosion resistance have been postulated: the concentration of carbon at the surface, or the enormous surface compressive stress. An electrochemical polarization curve was prepared for the plastically deformed gage length of a treated tensile specimen, to remove the effect of the residual compressive stress. This curve showed the same enhanced corrosion behavior, indicating that the enhancement is due to the high carbon concentration..

The graph shows cyclic polarization scans of treated and nontreated specimens of 316L in both 0.6M NaCl (a) and seawater (b). In each environment, pitting corrosion, normally the first indication of corrosion damage in this steel, has been completely suppressed by carburization. (The apparent pitting at high potentials actually is decomposition of the NaCl solution—Cl2 generation—as was confirmed by post-testing metallographic examination.)

Volume 4D, Heat Treating of Irons and Steels → Heat Treated High-Alloy Steels → Low-Temperature Carburization of Austenitic Stainless Steels → Performance Properties of the Low-Temperature Carburized Layer  → Wear Properties of the Low-Temperature Carburized Layer -> Corrosion Resistance

Subject Classifications

Materials Processing and Treatment | Heat Treating

Metals and Alloys | Carbon and Alloy Steels

Metals and Alloys | Stainless Steels

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