Using Some Mineral Salts (NaCl, KCl and CaCl2) as Chemical Inhibitors of Steel Corrosion at Presence Different Concentrations of Salts (Calcium Carbonate C.C, Sodium Nitrate S.N, and Potassium Phosphate P.P)

This study investigates the corrosion behavior of carbon steel (Calcium Carbonate C.C, Sodium Nitrate S.N, and potassium phosphate P.P) under different inhibitor concentrations (1%, 3%, and 5%) of some metal chloride salts (Sodium chloride (NaCl), Calcium chloride (CaCl?), Potassium chloride (KCl), and immersion periods (7, 14, and 28 days) using the weight loss method in accordance with ASTM G31. Natural plant extracts (pomegranate, seaweed, and potato peel) were evaluated as green corrosion inhibitors in chloride-containing environments. The corrosion rate (mm/year) was calculated based on mass loss, surface area, density, and exposure time. The results showed that corrosion rate is strongly influenced by inhibitor concentration, immersion time, and specimen diameter. In general, increasing inhibitor concentration from 1% to 3% significantly reduced corrosion rates due to improved adsorption of inhibitor molecules and formation of a protective surface film. However, at 5% concentration, some samples exhibited increased corrosion rates, suggesting possible instability or desorption of the protective layer at higher concentrations. Among the tested alloys, P.P and S.N generally showed better corrosion resistance than C.C, which recorded the highest corrosion rates under most conditions. Starch-based (or plant) extracts demonstrated the highest inhibition efficiency overall, followed by pomegranate extract, while seaweed extract showed moderate performance depending on concentration and exposure time. In several cases, zero corrosion rates or weight gain were observed, indicating the formation of stable passive films on the metal surface. Overall, the study concludes that an optimum inhibitor concentration exists, with 3% providing the best corrosion protection in most cases. The corrosion inhibition mechanism is mainly attributed to adsorption of phytochemical compounds containing heteroatoms and π-electrons, which form a protective barrier that reduces both anodic and cathodic reactions.