Comparative assessment and statistical data of admixed rosemary and castor oil on the corrosion inhibition of high carbon and P4 low carbon mold steels

Admixed rosemary and castor oil extracts (RSCO) were studied for their corrosion inhibition properties on high carbon steel (HCS) and P4 low carbon mold steel (P4S) in 1 M H2SO4 and HCl solution by coupon measurement. Results obtained showed that the admixed oil extract performed effectively on HCS and P4S with mean inhibition efficiency values above 90% for P4S and 80% for HCS in both acid solutions. The inhibition efficiency values of RSCO on P4S and HCS varied only with exposure time in H2SO4 with progressive increase in value compared to the effect of RSCO concentration which was negligible. The corresponding effect of RSCO in HCl solution showed no effect of exposure time and RSCO concentration on its performance on P4S while on HCS the effect of exposure time was observed. The standard deviation values obtained for RSCO inhibition efficiency at all concentrations on P4S and HCS in H2SO4, and HCS in HCl shows the degree of variation from mean values to be significant compared to the values obtained for P4S in HCl solution which were relatively small. The proportion of inhibition efficiency values above 70% inhibition performance are 39%, 44%, 100% and 39% at margin of error of 13%, 13.5%, 0% and 13% for P4S and HCS in H2SO4 and HCl solution. Analysis of variance shows exposure time is the dominant statistically relevant source of variation influencing RSCO inhibition performance in H2SO4 and HCl solutions. � 2021 Elsevier Ltd. All rights reserved