Influence of Nitrite and Molybdate Blend on Carbon Steel Inhibition in Chloride Containing Solutions

Abstract

Carbon steel inhibition has been managed by various methods of protection including cathodic protection, process control, reduction of the metal impurity content, and application of surface treatment techniques, as well as incorporation of suitable alloys. Inorganic and organic inhibitors are toxic and costly and thus recent focus has been turned to develop environmentally friendly inhibitors. Nitrites are now being increasingly used as environmental friendly inorganic corrosion inhibitor due to their low order of toxicity. Moreover, Nitrites are considered to be one of the most commonly used anodic inhibitors, shifting the corrosion potential to more noble values and consequently reducing corrosion. Molybdate based inhibitor has long been known as an inorganic and anodic type of corrosion inhibitor, which is effective for protecting mild steel. In order to achieve better efficiency and reduce the quantity of molybdate, we used a blend of nitrites and molybdates. In our work the experiments were conducted in the presence of NaNO2 with different concentrations in order to achieve the best efficiency values. Among the range of NaNO2 and Na2MoO4 concentrations used separately, at a lower concentration of 2 g/L efficiencies of 65% and 53% were achieved, respectively. However when molybdate was used as an additive, the blend at lower concentrations (2 g/L) resulted in 8.6 a synergism parameter, which indicates the synergistic effect of the mixture. The lower concentrations mixture of ratio 1:1 raised the efficiency to 93%.