Effect of an inhibitor on the stress corrosion cracking behavior of alloy 600 in a high-temperature caustic solution

The effect of cerium boride (CeB₆.) addition on the stress corrosion. cracking (SCC) susceptibility of Alloy 600 (UNS N06600) was investigated in a 40% sodium hydroxide (NaOH) solution at 315°C using slow strain rate tests (SSRT). Alloy 600, when strained at open-circuit potentials (OCP), failed completely in a pure ductile mode in the solution containing CeB₆, while the alloy was susceptible to intergranular stress corrosion cracking (IGSCC) in pure 40% NaOH solution. Polarization curves were measured for the same conditions. The corrosion current densities were estimated using the four-point method and the linear polarization method. The corrosion current density of the alloy in the 40% NaOH solution was significantly decreased by the addition of CeB₆ to the solution. The inhibition of IGSCC was attributed to the reduced corrosion current density.