| 摘要 |
PURPOSE:To prevent effectively the stress corrosion cracking of an Ni alloy used in an aqueous alkali soln. by an inexpensive and simple means even when the soln. is a concd. soln., by adding a small amount of MoO4<2-> or WO4<2-> to the aqueous alkali soln. CONSTITUTION:MoO4<2-> and/or WO4<2-> is added to an aqueous alkali soln. contacting with an Ni alloy by >=1X10<-5>mol/l in total. For example, said very small amount of MoO4<2-> and/or WO4<2-> is added to an aqueous alkali soln. which is passed through a pipe of ''Alloy 600'' used at high temp. and pressure. A strong and stable passive film is naturally formed on the inside of the pipe without requiring any special equipment or troublesome operation, so the stress corrosion cracking of the pipe can be surely prevented in said very inexpensive and simple manner even under severe conditions during alkali concn.
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