Stress corrosion cracking zirconium

Zirconium resists attack by nitric acid at concentrations up to 70 wt % and up to 250°C. Above concentrations of 70 wt %, zirconium is susceptible to stress-corrosion cracking in welds and points of high sustained tensile stress (29). Otherwise, zirconium is resistant to nitric acid concentrations of 70—98 wt % up to the boiling point. 

Zirconium is used in nitric acid service for cooler condensers, tail gas preheaters and reboilers. It rivals tantalum in its corrosion resistance to nitric acid at all concentrations up to the boiling point. Its resistance extends up to 230°C and 65 wt %. However it is susceptible to stress corrosion cracking, which can be prevented by avoiding high, sustained tensile stresses104. 

The environments, along with the cracking modes of zirconium and titanium, are given in Table 4.88. It is obvious from the table that zirconium alloys are susceptible to stress-corrosion cracking in a variety of environments. It is necessary to subject the weld to heat treatment in order to lower the stress in the weld. The most serious problem encountered in the nuclear applications is delayed hydride cracking in addition to stress-corrosion cracking, particularly in Zr-2.5% Nb alloy. 

Corrosion studies have been rare. (8), copper, or iron were corroded by carbon tetrachloride when exposed to Co-60 radiation (78). Alkyl halides enhanced the corrosive effect of benzoic acid on iron (79). (1) was found to promote stress-corrosion cracking in zirconium alloys used in nuclear reactors (80). 

S.B. Farina, G.S. Duffo, J.R. Galvele, Stress corrosion cracking of zirconium and zircaloy-4 in halide aqueous solutions, Corros. Sci. 45 (2003) 2497—2512. 

Zirconium and its alloys are susceptible to stress corrosion cracking (SCC) in such environments as Fe - or Cu -containing chloride solution, CH3OH -H hahdes, concentrated HNO3, halogen vapors, and liquid mercury or cesium [4,5]. Common test methods, e.g., U-bend, C-ring, split ring, direct tension, double cantilever, and slow strain rate tension, have been used to determine zirconium s susceptibility to SCC. 

Yau, T. L., Stress-Corrosion Cracking of Zirconium Alloys, Stress-Corrosion Cracking, R. H. Jones, Ed., ASM International, Metals Park, OH, 1992, pp. 299-311. 

Also soluble catalyst based on ethene bis(indenyl)zirconium dichloride/methylalu-minoxane can be used [519]. The C-NMR spectroscopically measured isotacticity is in excess of 97%, the molecular weight low (44 000), and the crystallinity 66.9%. Similar to polypropene poly(l-butene) crystallizes in four different modifications [520]. To influence the crystallinity, 1-butene was copolymerized with ethene or propene [521,522] or compounded [523,524]. Poly(l-butene) shows very good stability against stress, corrosion, cracking and is therefore used for pressure tubes. 

The stress corrosion cracking behaviour of X-750 can be considerably increased by a heat treatment at 760 °C/96 h in combination with improved strength, as tests in high purity water with pH 10 at 360 °C have shown [164]. As well, zirconium additions to the alloy improve the resistance to stress corrosion cracking, since the y ... 

Zirconium is susceptible to stress-corrosion cracking in concentrated hot nitric acid (Beavers et al., 1981 Kajimura and Nagano, 1992), iodine (Cox, 1990 Schuster and Lemaignan, 1992 Haddad and Dorado,... 

One of the most impressive corrosion properties for zirconium is its excellent resistance in HCl at all concentrations and temperatures even above boiling. Because of its strong reducing power, it is very difficult for most metallic metals to form protective oxide films in HCl. The presence of even a small amoimt of HCl in a medium may cause common metals and alloys to suffer general corrosion, pitting, and/or stress corrosion cracking (SCC). 

B.J. Fitzgerald, T.L. Yau, and R.T. Webster. 1992. Stress corrosion cracking of zirconium and its control in sulfuric acid. Corrosion 92, Paper No. 154, Houston, TX NACE Intemational. 

B.J. Fitzgerald and T.L. Yau. 1993. The mechanism and control for stress corrosion cracking of zirconium in sulfuric acid, in 12th Internatiorml Corrosion Congress, Houston, September 19-24. 

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