Investigating the Corrosion Resistance and Antimicrobial Behavior of Polyethylene-Silver Zeolite Composite Coatings on 304 Stainless Steel Substrate

Today, due to the presence of various microbial species and the reduction in healthcare costs, the use of antimicrobial materials has become indispensable for human society. Silver is the most widely used and effective antimicrobial agent, capable of penetrating bacterial structures and disrupting their biological systems. Among all methods of employing silver ions, the selection of zeolites, such as natural clinoptilolite with a crystalline aluminosilicate structure, hydrated, finely porous, and highly water-absorbent due to the ion release mechanism, has garnered significant attention. Heavy polyethylene is one of the corrosion-resistant polymers produced in Iran, offering insulation, quality, and cost-effectiveness. Due to its non-toxic nature and minimal environmental concerns, it has gained considerable attention. This research introduced silver ions into the porous zeolite network through an ion exchange mechanism. Subsequently, composite polyethylene coatings containing 0%, 10%, and 20% by weight of silver zeolite were applied on the 304 AISI stainless steel substrate using dip coating method. The coatings were then characterized through X-ray diffraction and scanning electron microscopy . The results indicated that with an increase in silver zeolite content within the polyethylene matrix, the coatings became more homogeneous, thicker, and corrosion-resistant. After applying the coatings, their corrosion behavior in a 3.5% wt.% NaCl environment was studied during 10, 24, 40, 70, and 100 days using electrochemical impedance spectroscopy. According to the results of electrochemical impedance spectroscopy, adding silver zeolite to polyethylene coatings up to 10 wt.% reduced corrosion resistance, while adding 20 wt.% increased corrosion resistance in the scratch-resistant coatings. Finally, by exposing the samples to a bacterial environment containing gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria, their antimicrobial properties were evaluated for potential antibacterial applications. The results from the halo and colony count tests suggested an improvement in antimicrobial efficacy against Staphylococcus aureus compared to Escherichia coli with increasing content of silver zeolite.