Iodine–β-Cyclodextrin: An Effective Corrosion Inhibitor for Carbon Steel in Sulfuric Acid Solution - Experimental Design and Investigating Thermodynamic Parameters

Widely used across industries, carbon steel is vulnerable to corrosion in aggressive environments, especially acidic ones. Thus, effective methods to mitigate metal corrosion from acids are crucial. Inhibitors are extensively used to prevent corrosion in industries, with the potential for improved protective performance. The design of experiments was employed to determine the optimal conditions for enhancing the inhibitor efficiency of Iodine–β-Cyclodextrin (Iodine/β-CD) in a sulfuric acid solution at temperatures ranging from 20°C to 50°C. The relationship between the factors and responses was established using response surface methodology (RSM), employing regression statistical analysis and probabilistic analysis. A single response was recorded: inhibitor efficiency was determined by measuring weight loss before and after immersion in the inhibitor solution. Thermodynamic parameters were also computed to determine adsorption and activation processes. The statistical analysis revealed that the quadratic models for inhibition efficiencies (IE) were highly significant with a coefficient of multiple regressions R2= 0.997. Further validation of the model indicated a good fit (R2 Adj= 0.994), and the experimentally observed values aligned well with predicted ones, demonstrating a highly significant model with Q2= 0.978. The theoretical efficiency predicted by the RSM model was 88.41%, whereas the efficiency observed during the experimental test procedure with the best-evaluated variables was 82.45%. In conclusion, this paper aims to identify the optimal conditions for employing Iodine–β-Cyclodextrin as a new corrosion inhibitor for carbon steel, utilizing experimental design methods. The results indicate that iodine/β-CD exhibits remarkable corrosion inhibitory properties for carbon steel under specific conditions.