Cathodic Protection Performance Evaluation of Magnesium Anodes on Mild Steel Corrosion in 0.5 M H2SO4 and Seawater Environments

Abstract

The performance of two different sizes of galvanic magnesium anodes on the cathodic protection of mild steel in 0.5 M sulphuric acid and seawater was evaluated at room temperature of 27 °C. The cathodic protection reactions process was observed by weight-loss method, its corresponding corrosion rate calculation and potential measurement method. The magnesium anodes were observed to be effective as sacrificial anode in the tested environments. In H2SO4, the experiment recorded very low weight loss of mild steel throughout the experiment. The magnesium anode with a larger cross-sectional area (magnesium anode 2) recorded a weight loss of 0.0095 g (9.5 mg) and corrosion rate (C.R.) of 0.007 mm/year; smaller size anode (magnesium anode 1) achieved 0.0785 g (78.5 mg) weight loss and C.R. of 0.062 mm/year during the same time of 21st day of the experiment. With magnesium anode 2 (bigger size) the potential ranged between − 0.467 V (− 467 mV) and − 0.441 V (mV) from the start to the end. For magnesium anode 1 (slightly smaller size) the electrode potential ranged between − 0.524 V (− 524 mV) and (− 0.441 V). In seawater environment, similar low value results were obtained. Mg (anode 2) recorded 0.0008 g (0.80 mg); the smaller anode (Ng anode1) recorded 0.0011 g (1.1 mg) weight loss at 21 days of the experiment. The results obtained for the potential measurement bear close correlation with the weight-loss method in both the sulphuric acid and seawater. The varying anode cross-sectional areas used showed the anode size effects.