The role of titanium in the initiation of localized corrosion of stainless steel 444

Localized corrosion: Understanding stabilised stainless steel Using a suite of techniques, the role of Ti-rich inclusions in the localized corrosion of stainless steel has been better understood. For some applications ferritic stainless steels are a good low-cost option because they contain low levels of relatively expensive nickel, however, they are vulnerable to intergranular corrosion. There are methods by which to minimize such unwanted corrosion chemistry, such as creating alloys with stabilizing agents like Ti and Nb. Now, a team, led by Janine Mauzeroll at McGill University, Montreal, Canada, has used a battery of techniques, such as X-ray energy dispersive spectroscopy and scanning electrochemical- and electron- microscopies, to understand the role of Ti-rich inclusions in the Ti-stabilized stainless steel ‘SS 444’. Specifically they found that, while Ti does improve bulk corrosion properties, Ti-rich inclusions act as initiation sites for localized corrosion

Corrosion properties of S-phase layers formed on medical grade austenitic stainless steel

The corrosion properties of S-phase surface layers formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C) has been investigated. The corrosion behaviour of the S-phase layers in Ringer's solutions was evaluated using potentiodynamic and immersion corrosion tests. The corrosion damage was evaluated using microscopy, hardness testing, inductive coupled plasma mass spectroscopy and X-ray diffraction. The experimental results have demonstrated that low-temperature nitriding, carburising and carbonitriding can improve the localised corrosion resistance of both industrial and medical grade austenitic stainless steels as long as the threshold sensitisation temperature is not reached. Carburising at 500°C has proved to be the best hardening treatment with the least effect on the corrosion resistance of the parent alloy