Silver Containing Stainless Steel as a New Outlook to Abate Bacterial Adhesion and Microbiologically Influenced Corrosion

Biofouling and microbiologically influenced corrosion (MIC) are alarming processes of material deterioration. The scenario originates from the attachment of microorganisms as quickly as a material is immersed in a non-sterile environment. Stainless steels, in spite of their wide use in different industries and as appliances and implant materials, do not possess inherent antibacterial properties. To make stainless steel antibacterial and thus to mitigate MIC and bacterial infection was the purpose of this study. AISI type 304 stainless steels containing silver as an alloying element and silver coated are tested for the antibacterial efficacy as well as MIC resistance keeping plain stainless steel as control. Experimental coupons were exposed to a dilute nutrient medium containing Pseudomonas sp., isolated from a corrosive ground water environment. Coupons were exposed for varying duration (maximum 6 days), and bacterial adhesion was monitored by using epifluorescence microscope and quantified with the help of image processing software. In another experiment, free corrosion potential of these materials was monitored for 60 days. The area of bacterial adhesion was found to be significantly lesser in case of silver containing coupons compared to control. Silver alloyed coupons showed better antibacterial effect than the silver-coated coupons. Free corrosion potential showed ennoblement in the case of control coupons, while silver alloyed and silver coated coupons showed substantially lesser fluctuation. SEM observation showed pitting corrosion by 30 days in control coupons, whilst, pits were near nil on silver alloyed and very less on silver coated coupons. The results, thus suggest that silver containing stainless steels possess antibacterial properties and are resistant to MIC as compared to 304 SS. Furthermore, a field study, where the coupons were exposed to a freshwater pond showed that coupons containing silver possessed significant resistance to microfouling build-up until a period of 30 days, suggesting the possibility of using these materials in freshwater environments where microfouling is a persistent problem. As an attempt to investigate the actual damage the silver caused in the bacterium, cell walls and intracellular changes were observed under a transmission electron microscope (TEM).