Selection of Corrosion Inhibitors and Their Corrosion Inhibition for 20 Steel in Wastewater Containing Methanol

Corrosion inhibitors of 20 steel in the simulated wastewater containing methanol were selected and optimized by weight loss method in order to slow down the corrosion rate of methanol recycle system, and their corrosion inhibition was studied by polarization curve method. The scale inhibition was investigated through energy dispersive spectroscopy (EDS) and scale inhibition testing. The results show that when the mass ratio of sodium tripolyphosphate to organic phosphorus A and to zinc chloride was 2:1:2, and the adding amount of compound corrosion inhibitor was 90 mg/L, the compound corrosion inhibitor showed the best inhibition with inhibition efficiency of 95.47%. The compound inhibitor was a mixed inhibitor which inhibited anodic reaction mainly. A protective film was formed on the surface of 20 steel from inhibitors containing phosphorus and resisted corrosive medium to corrode the substrate. The compound inhibitor also presented good scale inhibition, whose scale inhibition efficiency was 83.33%.