Lanthanum nitrate as corrosion inhibitor for low carbon steel in 3.5 wt. NaCl solution

Hexavalent chromes have been used as effective corrosion inhibitors due to their high efficiency and low cost for the protection of several metals and alloys. However, owing to their toxicity federal legislations restrict the use and distribution of these highly toxic materials. The need for an effective, environmentally friendly alternative to the chrome-based corrosion inhibitors has led to the investigation of rare earth metals as potential candidates. Owing to their low toxicity, the ingestion or inhalation of these inhibitors or their complex oxides/hydroxides is not considered harmful. From an economic standpoint, the use of these elements would be inexpensive due to their relative abundance in nature. Rare earth salts have been shown to be better environmentally acceptable replacements for traditional corrosion inhibitors for various metals in different corrosive environments. In this study inhibition effect of different concentration of lanthanum nitrate (La (NO3) 3) salt on corrosion behavior of low carbon steel in aerated 3.5 wt.% NaCl solution has been investigated via Open Circuit Potential (OCP), Potentiodynamic polarization and Electrochemical impedance spectroscopy (EIS) methods. OCP, EIS and Potentiodynamic polarization results showed that La (NO3) can decrease the corrosion rate of steel up to 80% at the concentration of 500 ppm. Furthermore, polarization curves revealed that La (NO3) acts as cathodic inhibitor, hindering the cathodic reaction.

Keywords:

Corrosion , Rare Earth , Inhibitor , Polarization