Effect of humidity on radiolysis-enhanced corrosion by gamma irradiation on electroless nickel plating

Abstract

The study reveals that water vapor can cause corrosion of electroless nickel plating under gamma irradiation, even in the absence of dew condensation. To control relative humidity during gamma irradiation, a simple apparatus utilizing saturated salt solutions was developed and validated by cold tests. Irradiation testing of electroless nickel plating was conducted under humidity control at relative humidity of 20%, resulting in surface degradation after 1 MGy total dose. Conversely, no degradation was observed on samples exposed to dry condition with relative humidity of less than 10% after a 5 MGy total dose. Humidity-uncontrolled irradiation tests, where condensation could occur, resulted in more severe corrosion than the humidity-controlled tests. A comparison of the chemical composition of corrosion products between the humidity-controlled and humidity-uncontrolled environments showed nitrate corrosion products were prevalent in the former while hydroxides were dominant in the latter.