Introduction

MOLTEN SALT BATHS are anhydrous, fused chemical baths used at elevated temperatures for a variety of industrial cleaning applications. Among the more common uses of these baths include:

• Removal of organic polymers and coatings

• Dissolution of sand, ceramic, and glassy materials

• Stripping of plasma carbide coatings

In addition, molten salt baths may be used to pretreat cast iron surfaces before brazing and bonding operations.

Molten salt baths for cleaning applications are chemically active or reactive fluids with unique process capabilities. They are quite distinct from other molten salt compositions that are used for simple heat transfer or heat treatment applications. Equipment requirements for successful use of these processes also differ from molten salt heat transfer or heat treatment equipment. Larger volumes of insoluble cleaning byproducts are usually formed that must be effectively and safely collected and removed from the baths.

Cleaning salt baths are formulated from a variety of inorganic chemical compounds. Among the more common ingredients are alkali hydroxides, alkali nitrates and nitrites, alkali chlorides, and alkali fluorides. By adjusting the ratios of the various ingredients, a wide range of melting points, operating temperature ranges, chemical reactivity, and other parameters can be obtained. As a whole, they offer combinations of reactivity, solvency, and speed unavailable in any other cleaning medium. The chemistry involved during various cleaning applications ranges from simple dissolution of contaminants to more complex reactions involving the thermochemical oxidation of organics and the electrolysis of molten salts.

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