LAUSR

Abstract The corrosion inhibition effect of non-toxic calcium gluconate at 0.75%, 1.25%, 1.75% and 2.25% concentration on mild steel in artificial seawater (3.5% NaCl) was studied by potentiodynamic polarization, coupon measurement, optical microscopy characterization and open circuit potential measurement. Results obtained showed the inhibiting compound effectively suppressed the corrosion of mild steel with inhibition efficiency value generally above 80% from polarization test and 90% from coupon measurement after 0.75% concentration of calcium gluconate. Calcium gluconate exhibited mixed type inhibition property with dominant anodic inhibition effect. The inhibitor adsorbed onto the steel surface through physisorption mechanism according to Langmuir and Frumkin isotherm models. Calcium gluconate shifted open circuit corrosion potential plot of mild steel to electropositive values compared to the plot of the non-inhibited steel. Corrosion pits in addition to severe worn out morphology on the image of the non-inhibited steel were absent on the inhibited steel with relatively improved surface morphology.