Abstract
Corrosion behaviour of stainless steels in wet process phosphoric acid has been studied by immersion tests and electrochemical measurements. Effects of fluoride, chloride, sulfate and other impurities, which are usually present in the wet process phosphoric acid, have been also investigated in the present work. The increases in chromium and molybdenum contents of the stainless steel generally improved a corrosion resistance to the wet process phosphoric acid, and in particular those containing chromium above 20% and molybdenum above 2% showed the highest resistance among the stainless steels tested.
The transition from passive to active corrosion can be induced by increasing the fluoride or chloride concentration to an overcritical level, which results in a high corrosion rate.
