Cathodic Protection of Aluzinc coated, Galvanized and Stainless Steels in Ijegun Seawater using Aluminium as Sacrificial Anode
Cathodic protection is an electrochemical method of controlling corrosion on metallic structures which are in electrolytes. Safety and environmental aspects of corrosion are difficult to quantify in terms of costs but are known to have put people’s lives at risk hence this research aimed at the study of cathodic protection of aluzinc coated, galvanized and stainless steels with aluminium as the sacrificial anode in Ijegun seawater. The samples (300 x 50 x 2 mm3) were connected independently to the sacrificial anodes of Al with cables and then submerged in Ijegun for 16 weeks. All samples were characterized by Scanning Electron Microscope. The corrosion rates were determined by gravimetric and electrochemical impedance spectroscopic methods. The gravimetric method results showed the corrosion rate of protected samples: stainless, galvanized and aluzinc coated steels were 2.54E-4, 4.84E-4 and 1.80E-3 mm/yr respectively while the control samples were 5.36E-4, 9.55E-4 and 3.97E-3 mm/yr in that order. The electrochemical impedance spectroscopic results obtained for protected stainless, galvanized and aluzinc coated steels were (629.351, 685.575), (268.786, 253.498) and (216.3464, 58.380) Ω respectively while the control samples were (527.417, 299.112), (188.150, 91.259) and (66.3077, 24.022) Ω in that order. The scanning electron microscope results showed thicker masses on unprotected than protected samples. The methods used revealed that, stainless steel had the highest resistance to corrosion while aluzinc coated steel had the least resistance. Conclusively, cathodic protection method using sacrificial anode of aluminum is effective in protecting steels in marine environment.