Zirconium is one of a very few materials of construction for processes involving high concentrations of
sulfuric acid at temperatures above the atmospheric boiling point. In this severe environment only
zirconium or tantalum can be used with any reliability. Most corrosion data for zirconium has been
developed using welded wrought material as test coupons. The majority of this information is related to
the corrosion resistance of Zr 702 with very little information available for Zr 705. In addition, almost no
information is available as to the corrosion resistance of the cast forms of either alloy. This paper
presents laboratory data comparing the corrosion resistance of Zr 702 and Zr 705 in the welded and
wrought forms and in the cast form in sulfuric acid. A newly expanded iso-corrosion diagram is
presented for both wrought and cast Zr 702 and Zr 705. Zr 705 is a zirconium alloy containing 2.5%
Niobium. Because of the possibility of hydrogen absorption by the Niobium phase during the corrosion
process, hydrogen absorption data is also presented for Zr 705. This hydrogen absorption data is
compared with Zr 702 tested under the same conditions.
KEYWORDS: Zirconium, Zr 702C, Zr 705C, Zr 702W, Zr 705W, corrosion, sulfuric acid, metallurgical, mechanical,
safety, UNS R60702, UNS R60705, iso-corrosion, hydrogen analysis, cast