Corrosion inhibition of aluminum alloy by a sodium alginate-based composition in a neutral chloride-containing environment

The inhibition of corrosion of an aluminum alloy in a neutral chloride-containing environment was studied using an environmentally friendly composition based on sodium alginate and zinc acetate. The study found that the anti-corrosion efficiency of the composition reached its maximum when the components were present in equal proportions, providing a metal protection degree of 85–95%. Alginate molecules, due to their hydroxyl and carboxyl functional groups, adsorb onto the surface of the aluminum alloy and form poorly soluble complex compounds with Zn2+ cations released during the dissolution of zinc acetate. Consequently, the adsorbed alginate film becomes denser, enhancing its protective properties. Protective layers of zinc hydroxide form on the cathodic regions of the aluminum alloy, effectively slowing down the oxygen reduction reaction. Additionally, acetate ions exhibit anti-corrosion properties through their ability to adsorb onto the metal surface. The formation of a protective film on the alloy surface in inhibited solutions was confirmed by electrochemical impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis.