Experimental and theoretical investigations on the inhibition of mild steel corrosion by capsaicin derivatives in hydrochloric acid

The protective properties of two capsaicin derivatives named N,N'-((4-hydroxy-2,5,6-trimethyl-1,3phenylene)bis(methylene))diacrylamide and N,N'-((5-chloro-2,4-dihydroxy-1,3-phenylene)bis(methylene)) diacrylamide in hydrochloric acid for mild steel were investigated. Electrochemical experiments showed that the inhibition efficiency of the two capsaicin derivatives as mixed inhibitors reached 96.24% and 93.71% at 0.3 g/L, respectively. Surface observations show that the capsaicin derivatives adhere firmly to the mild steel by forming a barrier. These two inhibitors fit the Langmuir adsorption isotherm and mixed adsorption type. The computational studies (DFT and MD) provide excellent support for the experimental results of both inhibitors.