Sulfamic acid as pickling agent for zinc and iron based alloys and its corrosion inhibition using inhibitors: a comprehensive review

Pickling agents such as sulfamic acid (NH₂SO₃H) are favoured due to their distinct ability to break down tough deposits and scales. Sulfamic acid is less corrosive than other acids, such as hydrochloric, sulfuric and nitric acids, and it does not release any toxic fumes when used. Nevertheless, even though it is a mild acid, it can lead to deterioration of many metallic materials in its lower pH range; hence, it needs to be regulated to enhance its corrosion resistance. Therefore, organic compound-based corrosion inhibitors of natural and synthetic origin are widely used to prevent corrosive damage to metallic surfaces in such electrolytes. Recent studies on the corrosion inhibition behaviour of various zinc and iron-based alloys in sulfamic acid media using various inhibitors are included in this article. The various techniques employed to explore the electrochemical behaviour of these materials in the presence of various inhibitors and their inhibition potentials are discussed. Additionally, the corrosion characteristics of steel and zinc in sulfamic acid and the interaction of inhibitor molecules with the metal surface, and mode of adsorption are also discussed in detail.