Thiazolium-Bearing Chitosan Polymer Mitigates Microbiologically and Acid-Induced Corrosion on Stainless Steel Dental Crowns and Pipeline Steel in Saliva and Pickle Liquor

Abstract

Microbiologically and chemically induced corrosion episodes degrade metal alloys, weaken their mechanical strengths, and lead to loss of constituent contents when these alloys interact with their surrounding environments. While metallic dental materials (e.g., stainless steel dental crowns) are highly susceptible to pitting corrosion induced by bacterial (e.g., Porphyromonas gingivalis) biofilms within the oral cavity, pipeline steels can also significantly corrode in their service environments (e.g., during surface pickling or product transportation). Due to toxicity concerns, using safe and environmentally sustainable corrosion inhibitors has become a protective strategy for most metal alloys in place of chromates. The present study introduces a cationic thiazolium-bearing chitosan (CTBC) derivative utilized as an antimicrobial and inhibitor against microbiologically and acid-induced corrosion of coarse-grained 316L stainless-steel dental material and fine-grained ×70 pipeline steel, respectively. Due to the thiazolium-bearing moiety, this water-soluble chitosan polymer, with its unique antimicrobial activity against P. gingivalis, an oral Gram-negative pathogenic anaerobe, demonstrated an impressive level of enhanced biocorrosion inhibition for stainless steel dental material in saliva. Importantly, this polymer also significantly protected against ×70 pipeline steel corrosion compared to normal chitosan in pickle liquor. This instills confidence and sparks optimism about its potential applications in protecting metal alloys. Lower magnitudes of corrosion current density (j corr ) were recorded for crown and pipeline materials in salivary culture and pickle liquor containing 100 ppm of CTBC relative to chitosan at equimolar concentration. A reverse trend was recorded for charge transfer resistance (R ct ); higher R ct values denote polymer adsorption on pipeline steel. Over 90% corrosion inhibition efficiency was recorded for stainless steel substrates exposed to the salivary test culture with growing bacterial cells and ×70 steel substrates in the pickle liquor with 500 ppm of CTBC.