Abstract
The corrosion resistance of a number of stainless steels and nickel alloys in solutions of pure phosphoric acid boiling under reflux and in similar solutions under conditions of heat transfer has been investigated. The effect of phosphoric acid concentrationand alloy composition on the corrosion rates obtained has been evaluated. The effect of additions of impurities such as fluoride, chloride, silicate and ferric ions on the corrosion behaviour of a number of the alloys in concentrated phosphoric acid under conditions of heat transfer has also been determined; such impurities are often present in wet-process plant phosphoric acid at the evaporator stage. The work has demonstrated that the alloys of highest nickel content generally exhibit the best corrosion resistance in such environments. It has also been shown that whilst chloride ion additions considerably increase the aggressive nature of the environment, fluoride additions in general have very little effect.
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