Utilization of Sodium Polyacrylate Hydrogels in the Sacrificial Anode Cathodic Protection Method for Steel Members at the Atmospheric Environment

To achieve sacrificial anode cathodic protection (SACP) for steel members in the atmospheric environment, the sodium polyacrylate hydrogels were prepared and acted as electrolyte carriers in the protection system. The hydrogels absorbing varying concentrations of sodium chloride solution were verified by the water swelling and retention test, the electrochemical test, and the constant exposure test. The result shows that the hydrogel shows a remarkable water absorption capacity with the NaCl solution. However, within 48 h, little difference shows in the swelling ratio. And the water retentivity weakens with the concentrations of sodium chloride solution increasing up to 3.5 mass%. The hydrogel absorbing 10.0 mass% sodium chloride solution exhibits the highest retention ratio. Moreover, the steel specimens immersed in the hydrogel show greater resistance to corrosion compared to exposure in NaCl aqueous solution. Besides, the SACP method using the hydrogel can sustain corrosion protection for over 200 h, based on the time-dependent anti-corrosion current density, which ensures the durability of the system. Overall, the findings suggest that sodium polyacrylate hydrogels demonstrate promising attributes as electrolyte carriers, broadening the potential application of the SACP method to atmospheric environments.