MILD STEEL CORROSION INHIBITION IN ACIDIC WATER ENVIRONMENTS WITH SODIUM NITRATE: AN UP-TO-DATE RESEARCH PROGRESS REVIEW REPORT

Corrosion inhibitors are effective alternatives for protecting steel from corrosion in aqueous environments. Synthetic corrosion inhibitors pose serious global environmental issues and health risks; nevertheless, a few of them have excellent environmental properties, handling safety, and very high corrosion inhibition efficiencies. This study presents an up-to-date literature review on sodium nitrate as an inorganic synthetic corrosion inhibitor of mild steel in acidic water environments, showcasing its general uses, properties, safety level, availability level, cost, and research advances as integrated knowledge for research gaps and progress on its corrosion inhibition studies. The review shows that mild steel is the topmost structural metal for engineering systems due to its greater versatility in terms of outstanding strength, fabrication properties, affordability, widespread use, and sustainable availability around the world, but it has very low corrosion resistance. It contributes to approximately 90% of all steel types and 90% of all corrosion problems worldwide. Acidic water environments are highly aggressive and capable of rapidly corroding mild steel electrochemically, leading to its significant weight loss, structural integrity reduction, and failure possibility with unpredictable hazardous consequences. The review also shows that corrosion inhibition efficiency of mild steel with sodium nitrate can vary greatly depending on the corrosivity extent of the environment. Sodium nitrate best inhibits mild steel corrosion in industrial environments at optimized concentrations ranging from 75 mg/L to over 1000 mg/L. The corrosion inhibition of mild steel with sodium nitrate is mostly focused on neutral-to-alkaline and oxygenated water environments, such as simulated cooling waters, concrete pore solutions, and industrial cleaning solutions, but is greatly unresearched in several natural acidic waters, including sour waters; highly saline, especially chloride, waters; and high-flow-velocity waters at ambient and higher temperatures.