Salt Bath Descaling

The removal of oxide scale can be accelerated by using baths of molten sodium hydroxide (NaOH) to which certain reagents are added. These baths can be used with virtually all grades of stainless steel. Salt bath descaling has several advantages:

• It acts only on the scale and does not result in metal loss or etching.

• It does not preferentially attack areas in which intergranular carbides are present.

• It is particularly useful in descaling the straight chromium grades without the preliminary sandblasting that is frequently required prior to acid descaling.

Use of molten salts is not recommended for those stainless steels that precipitation harden at the operating temperature of the bath. Procedures and equipment for descaling in molten salt are described in the article "Molten Salt Bath Cleaning" in this Volume.

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