Zirconium is one of the few metals that resists attack by sulfuric acid (H²SO⁴) up to 75% concentration. It is being frequently used to handle the acid in the difficult concentration range of 40 to 60%. However, due to environmental concerns, the dumping and the storage of H²SO⁴ wastes have become a problem. Contaminated H²SO⁴ is involved in many processes. The purpose of this investigation is a more precise characterization on the effects of impurities on the corrosion resistance of zirconium.

Corrosion behavior of zirconium alloys in H²SO⁴ with common detrimental impurities, that is, Fe⁺³, Cu⁺², Cl⁻, NO3−, and seawater, has been investigated. It has been found that Zr 702 and Zr 704 can tolerate a larger amount of impurities than Zr 705. Welds of zirconium alloys are susceptible to local corrosion in contaminated H²SO⁴. However, the local corrosion of welds can be easily avoided by a proper that treatment. For our corrosion tests, the heat treatment was performed at 760°C for 15 min.

The performance of passivated Zr 702 and Zr 705 under a simulated upset condition, for example boiling 74% H²SO⁴, has been studied. It has been found that Zr 702 can withstand the upset conditions without significant attack up to 20 min, but Zr 705 will corrode immediately and rapidly.