Enhancing the passivity of 316l stainless steel by low-temperature nitriding

Abstract:

Low-temperature nitride synthesis route was used to introduce interstitial nitrogen into as-received and as-polished 31 6L stainless steel samples. The samples were treated in an ultra pure nitrogen atmosphere at 450 °C. The corrosion protection afforded by nitride coatings formed on stainless steel substrate, has been studied using dc polarisation and ac impedance techniques. An enhanced passivity of the nitrided stainless steel was detected even after two weeks of immersion in a 3.5% NaCl solution. The as-polished samples treated at 450 °C in nitrogen showed the highest corrosion resistance. The polarization resistance (Rn) for the blank alloy was measured by EIS to be approximately 6.5× 103 Ω.cm2. The Rp increased by a factor of 7-8 for the nitrided samples. Increasing the nitriding temperature from 450 to 650 °C affects the negatively the corrosion resistance in NaCl. The Rp decreased sharply to be 1.1×103 Ω.cm2 which is almost one sixth of the Rp of the blank samples. SEM-EDS were used to examine the nitride coatings formed on stainless steel substrate under different conditions. The nitride films formed were analysed before and after corrosion using XRD.

Año de publicación:

2009

Keywords:

Fuente:

scopus