Effects of polyethylene glycol (PEG) on the corrosion inhibition of mild steel by cerium nitrate in chloride solution

International audienceIn this study, cerium was investigated as an inhibitor to improve the corrosion resistance of ASTM A915 mild steel in 0.1M NaCl solution. Increasing the Ce 3+ concentration up to an optimum level of 600 mg.L-1 (or 1.4 10-3 M) sharply decreased the corrosion rate (Icorr). However, the beneficial effect of cerium was lost after short immersion times at room temperature. In contrast, the addition of polyethylene glycol (PEG) to the cerium nitrate containing NaCl solutions enhanced protection through the formation of stable corrosion products and the decrease of cracks in the film formed on the surface of mild steel

On the Corrosion Resistance of Porous Electroplated Zinc Coatings in Different Corrosive Media

The corrosion resistance of an electroplated (EP) Zn coating whose surface was chemically etched to produce surface defects (pores) is investigated in this work. Impedance and DC polarisation measururements were employed to study the behaviour of such coating in various corrosive media (NaCl, NaOH and rain water). Four different faradaic relaxation processes were clearly revealed in different NaCl concentrations (from 0.1M to 1M). In the most concentrated solutions at least three relaxation processes at low frequencies (LF) appeared and were related to zinc deposition and dissolution. At lower concentrations and depending on the pH, only one process was observed. The charge transfer resistance (Rct) and the corrosion current (Icorr) were practically stable in the pH range 5 to 10. In deaerated NaCl 0.1M, the EIS diagrams showed two time-constants at very close frequencies. From the EIS diagrams the porous nature of the coating was highlighted and showed that the dissolution mechanisms occurred at the base of the pores