High Temperature And Corrosion Inhibitor For Carbon Steel In Mud Acid Medium

This paper studied the corrosion velocity and corrosion inhibition efficiency of mild steel in 5% mud acid with a few of compounds by weight-loss method, then three kinds of compounds with good corrosion inhibition effect have been got in mud acid solution, including alkynol, quaternary ammonium and heterocyclic compound. In these compounds propiolic alcohol,butynediol,benzalkonium chloride,benzalkonium bormide and cetyl pyridinium bormide were selected as research object. Their corrosion inhibition action of mild steel was studied with different temperatures in mud acid solution by adsorption theory and electrochemical polarization-curve method, the mechanism of corrosion inhibition action was analyzed. The result shows that the single molecule layer of these compounds adsorbed on the surface of the mild steel and followed Langmuir isothermal equation. The adsorption procedure was exothermic reaction, the adsorption ability and corrosion inhibition efficiency decreased when temperature increased. At 80℃, their corrosion inhibition efficiency are 94.93%, 86.06%, 97.13%, 95.93% and 97.71%. They are all mixed type inhibitor except that cetyl pyridinium bormide is anodic type inhibitor. The corrosion current was decreased by them in different degree. These compounds used respectively have low corrosion inhibition efficiency in high temperature and can't meet practical require. So a composite corrosion inhibitor with excellent corrosion inhibition efficiency was composed by orthogonal method, corrosion inhibition action of this composite corrosion inhibitor has been evaluated. The corrosion rate of mild steel in mud acid has been determined with different temperature, different concentration of mud acid, different time and different concentration of iron ion. The SEM photos of mild steel surface have been taken under different corrosion condition. The experiment testified the composite corrosion inhibitor is an anodic type inhibitor. When temperature was 80℃, the concentration of mud acid solution (HCl:HF=7:3) was 20%, the reaction time was 24 hours and the concentration of Fe3+ ion was 1000ppm, the corrosion velocity of steel accorded with national standard(﹤6 g·m-2·h-1). It shows this composite corrosion inhibitor possess excellent corrosion inhibition of anti-temperature, anti-acidity, anti-time, anti- Fe3+ion and anti-nonuniform corrosion, it's an excellent high-temperature corrosion inhibitor in mud acid solution.