Study on Necessary Conditions of Flux for Aluminizing, and Adaptability of Salts and Compounds as Flux, for Hot Dipping Process of Steel with Aluminum

Abstract

In order to find out useful fluxes for aluminizing, cleaning action of fluxes for oxide films on steel surface, solubility of Al₂O₃ as flux, and the fluxing effect in the boundary of steel and molten aluminum in case of dipping, were examined using chloride, fluoride, boride, carbonate, etc.
As a result, it may be concluded that the flux for aluminizing should satisfy the following conditions:
1. The steel surface should be wet.
2. The Al₂O₃ film should be removed by dissolving.
3. Flux should free from the aluminum-steel boundary.
4. No gas film forming in the aluminum-steel boundary is allowed.
5. No degrading aluminum purity is allowed.
The flux of the eutectic composition of KF-AlF₃ system (54.2% AlF₃) is most excellent, and next comes the flux of NaF-AlF₃ system.