The corrosion of zirconium in HCl was studied at 150-250 C in aqueous solutions containing 5 to 37 percent by weight of HCl. Studies of the dependence of the corrosion rate on temperature and time were conducted, and the experimental data correlated with studies of the corrosion products, surface films, and the metallurgical structure and chemical composition of the substrate. The kinetics are also given.
Hydrogen was found to play an important role in the corrosion mechanism as a surface coating of zirconium monohydride and dissolved in the zirconium lattice.
Initially, an accelerating corrosion rate was found with time, followed by a transition to a decreasing corrosion rate. It was concluded that the corrosion mechanism was controlled by the initial reaction up to the transition point, beyond which it is suggested that the reaction is either diffusion controlled and/or influenced by hydrogen adsorbed at the surface.
Intergranular corrosion of alpha-annealed zirconium and attack at both the grain boundaries and between the alpha needles of beta-treated furnace cooled zirconium were observed at the higher temperatures. The beta-treated furnace cooled zirconium was more resistant to attack by HCl than the alpha-annealed zirconium.
Much improved corrosion resistance to HCl may be expected with higher purity metal. In this respect the zirconium used in this study does not represent the higher quality metal being produced today by advanced processing, melting and fabrication techniques. 6.3.20
