The deviation in potentials to passivation potentials in H2SO4 and HCl depicts the improvement of the corrosion resistance of the steel with NNDT addition due to physiochemical interaction of the NNDT molecules unto the steel surface.
The electrochemical effect of NNDT on the corrosion polarization curves (anodic and cathodic) for mild steel in the acid media was investigated.
25% NNDT concentration due to the presence of significant amount NNDT molecules to compete with and inhibit the electrochemical actions of the corrosive anions, block the active sites and form a protective film on the alloy surface in the acid solutions.
NNDT significantly affects inuences the dynamics of the electrochemical reactions modifying the anodic dissolution of the metal in the acid solutions through adsorption.
Due to the innate protonated hydrophilic amino and imino groups NNDT strongly adsorbs on the ionized steel surface, while their hydrophobic substituent (thiol) aligns the NNDT molecules during adsorption to form a protective film that shields the steel from the acid media.
Scanning electron micrographs of mild steel topography before and after weight loss test in acid solutions and after 432 h exposure time at predetermined concentrations of NNDT are shown in Fig.
The scanning electron microscopy image of the steel sample with NNDT as shown in Fig.
The X-ray diffraction (XRD) patterns of the sample surfaces after exposure hours in the acid solutions in the presence and absence of NNDT are shown in Fig.
5 M H2SO4 solutions with NNDT showed the absence of chemical compounds/corrosion products associated with corrosion.
Table-9: Analysis of variance (ANOVA) for inhibition efficiency of NNDT inhibitor in 0.
Table-10: Analysis of variance (ANOVA) for inhibition efficiency of NNDT inhibitor in 0.
Two-factor single level experimental ANOVA test (F-test) was applied to investigate the isolated and cumulative outcome of NNDT concentrations and exposure time on the %IE of NNDT in the corrosion of inhibition of mild steels in both acid solutions and to investigate the statistical connotation of the outcomes.