Effects of 4-bromoaniline and pentylamine compounds on the stress corrosion cracking of mild steel and brass in dilute electrolyte solutions

Abstract

The inhibition effect of 4-bromoaniline (4BA), pentylamine (PTL) and their combined admixture on the stress corrosion behaviour of mild steel and brass in 0.5 M and 0.3 M H2SO4 and NH4OH solution was studied through open circuit potential measurement and visual observation. The experiment was performed at 90% stress level for optimal results. Results obtained showed that the inhibitor compounds generally influenced the thermodynamic tendency of the alloys to corrode, delayed the onset of crack formation and specimen failure in the electrolytes. The combined admixture of 4BA and PTL performed most effectively in the both acid solutions, increasing the corrosion potential to -0.391 V and -0.281 V compared to the corresponding values obtained in the control acid solutions at -0.446 V and -0.451 V. 4BA performed most effectively in NH4OH solutions with corrosion potential values of -0.743 at 504 h. Visual observation of the metallic alloys shows crack initiated on mild steel in both acids without inhibitor addition at 72 h of exposure and specimen failure occurred at 216 h. The corresponding observation for brass in 0.5 M NH4OH solution showed crack initiated at 144 h before failure at 360 h. In 0.3M NH4OH, crack initiation and failure occurred at 216 h and 504 h respectively. The admixture of 4BA and PTL delayed crack initiation on mild steel to 216 h and no specimen failure was observed at 504 h. 4BA delayed the onset of crack formation on brass in 0.5 M and 0.3 M NH4OH solution to 216 h and 288h. However, failure occurred at 432 h in 0.5 M NH4OH compared to no failure at 504 h of exposure in 0.3 M NH4OH solution.