Inhibitive effects and mechanism of phosphates on the stress corrosion cracking of brass in ammonia solutions

The stress corrosion cracking (SCC) behavior of H62 brass in Mattsson’s solution containing various concentrations of disodium hydrogen phosphate (DHP) was investigated by slow strain rate tests and electrochemical tests. The results confirm that the susceptibility of brass to SCC and film-induced stress decreased with increasing DHP concentrations. Electrochemical measurements show that DHP inhibits SCC by forming a copper phosphate and zinc phosphate film on the brass surface. This film, in turn, inhibits the formation of the tarnish film and dezincification and decreases film-induced stress, thereby restarting the film formation and reducing the susceptibility of brass to SCC.

► Potentiodynamic polarization revealed that Na2HPO4 suppress anodic dissolution.
► Susceptibility of brass to SCC decreased with increasing DHP concentration.
► Film-induced stress changed from tensile to compressive as DHP increased.
► The relation between SCC susceptibility and corrosion-induced stress was proposed.