Study on the corrosion inhibition performance of sodium silicate and polyaspartic acid for 35CrMo steel

Silicate is widely used as a water-based corrosion inhibitor due to its non-toxic, environment-friendly, and low price. It can form a Si-O-Si film on the metal surface to protect the metal from being corroded. However, the rough and porosity sodium silicate film would result in localized corrosion. In addition, sodium ions dissociate between the Si-O-Si network, enabling the absorption of CO2 from the atmosphere and forming white points on the surface of the film. Therefore, using sodium silicate alone as a corrosion inhibitor is not ideal. In this work, 35CrMo steel was adopted as the protected material. The corrosion protection effect of PASP (polyaspartic acid) and sodium silicate compound water-based rust corrosions, which contain 10 mg/L, 15 mg/L, 20 mg/L, and 25 mg/L PASP, respectively, were systematically studied. Specifically, tem- perature, and humidity accelerated corrosion test, brine immersion test, electrochemical impedance spectroscopy and linear polarization measurement were utilized. The results showed that the water-based corrosion inhibitors with different PASP contents have a specific protective effect on 35CrMo steel. The protective effect accumulates roughly with the increase of PASP addition, and the highest is achieved when the PASP content reaches 20 mg/L. However, when the PASP content reaches 25 mg/L, competitive adsorption between PASP and sodium silicate reduces the corrosion inhibitor effect.