Colouring process for ferritic stainless steel alloy in NaNO3-KNO3 eutectic melt
✍ Scribed by H. A. Abdel-Hakim Ali; S. A. Abdel Gwad; A. N. Al Masri; Prof. Dr. A. M. Baraka
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 446 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0933-5137
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✦ Synopsis
Abstract
The colouring process of the ferritic stainless steel alloy (15.03 Cr) was carried out in pure NaNO~3~‐KNO~3~ eutectic melt and in presence of Na~2~O~2~, NaCl and their mixtures at different temperatures (673–873 K) under open‐circuit and galvanostatic anodic polarization conditions. Coloured oxide films can be formed and the colours greatly depend on the thickness which in turn depends on the composition of the molten bath and its temperature. The more attractive, bright, adherent and uniform coloured films can be formed at temperatures of 673, 723 and 773 K in the nitrate melt containing Na~2~O~2~ and mixtures of 0.5 M NaCl with Na~2~O~2~ additions. The corrosion tests, carried out on the coloured oxide films in 0.1 M HCl solution, show that the corrosion resistance of the coloured films greatly depends on the previous operating conditions of the colouring process such as composition of molten bath and its temperature.