Optimization of inhibition performance of hexa methylene tetra amine for corrosion of mild steel in CO2-saturated brine produced water

The performance of hexa methylene tetra amine (HMTA) (C6H12N4) as a corrosion inhibitor for mild steel in simulated CO2-saturated brine solution was investigated in the absence and presence of inhibitor at various HMTA concentrations, temperatures, and velocities using weight loss technique. Doehlert Experimental Design (DED) was used for designing of experiments. A second order polynomial equation with main, quadratic and interactive influences was suggested and optimized. Nonlinear regression statistical analysis was used for estimation of polynomial coefficients based on Quasi-Newton & Rosenbrock method. Inhibitor concentration showed a high positive impact in reducing the corrosion rate, while temperature and mixing velocity showed the negative effect. The optimum (minimum) corrosion rate was 18.714 gmd at 35.69 °C brine temperature, 74.47 ppm HMTA concentration, and 163.12 rpm mixing velocity. At these optimum conditions a 92% inhibition efficiency was obtained.