Soluble sodium silicates have a complex chemistry. Thirteen compositions were selected from the phases known to exist at 300 C, and U-bends of welded Alloy 600 were tested to determine which compositions caused the most rapid stress corrosion cracking. Highest cracking rates of 2.4 × 10−4 in./h were observed at a composition of 16/12/72 mol% Na2O/SiO2/H2O. No stress corrosion cracking was observed in 175 h tests with polymeric silicates present. Alloy 690 was also found to be subject to stress corrosion cracking in the 16/12/72 composition.
National Association of Corrosion Engineers
1985
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