Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Influence of Phosphorus, Sulpher and Oxygen on 65% Nitric Acid Corrosion Resistance of Super High-clean SUS316L Stainless Steel
Kazuyuki SAKURAYATakashi KIMURASatoshi IWASAKI
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JOURNAL FREE ACCESS

2005 Volume 91 Issue 6 Pages 560-566

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Abstract

For the purpose to verify the effect of decreasing phosphorus on corrosion properties of stainless steels, corrosion resistant tests in 65% nitric acid solutions were carried out for super-low phosphorus content SUS316L type stainless steels which were manufactured by cold crucible type levitation melting method using Ca-CaF2 flux for aiming at the dephosphorization. By decreasing phosphorus content in these steels from 0.026 to 0.0002 mass%, the corrosion rate in 65% nitric acid solutions decreased remarkably. Especially even under 0.001% phosphorus content, this decreasing phenomenon could be observed. Thus extreme dephosphorization improves the corrosion resistance of stainless steels marvelously.
As for the non-metallic tramp elements, there were linear relations between corrosion rate and the very small amount of sulfur and oxygen contents in the super-low phosphorus stainless steels containing under 0.0002 mass% phosphorus. So the super high purification of these elements is also very effective for the improvement of corrosion resistance against nitric acid solutions.
It is known that the corrosion of austenitic stainless steels containing over 0.003 mass% phosphorus in nitric acid solutions is intergranular corrosion. In the present work, it is confirmed that the corrosion of super-low phosphorus content SUS316L type stainless steels even at 0.0002 mass% is not uniform corrosion but intergranular corrosion.

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© The Iron and Steel Institute of Japan
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