Escherichia coli (ATCC 25922) induced corrosion in Zn-Ni-Cu and Zn-Ni-Cu- TiB 2 coated ASTM A-36 Steel

Abstract

The study aimed to investigate the corrosion performance of Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ coatings in the microbial-induced environment (E-Coli, ATCC 25922, and 3.5%NaCl solution). Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ were surfaces coated on an ASTM A-36 Steel substrate utilizing a high-velocity oxy-fuel (HVOF) thermal spray process. Immersion tests following ASTM G-31, and ASTM G1-03, standards were performed in Escherichia Coli (E-Coli, American Type Culture CollectionATCC25922) bacteria medium.The effect of Zn, Ni, and Ti was studied in preventing microbial-induced corrosion.SEM, and XRD analysis before and after helped to understand the morphological and structural changes in coated/uncoated ASTM A-36 steel. Various forms of rust were ascertained in XRD analysis. The presence of Zn and Cu prevented the bacterial attachment with coated surface and hence prevented the underlying substrate from being corroded substantially.The coatings performed well and limited the growth of bacteria. The uncoated ASTM A-36 Steel specimen showed well-developed bacterial colonies on the surface and in the solution medium. All forms of rust were reported in XRD analysis for uncoated ASTM A-36 steel while few forms of rust were reported in coated ASTM A-36 steel.Tafel polarization and electrochemical impedance spectroscopy (EIS) in Escherichia Coli (E-Coli, ATCC 25922) medium confirmed that coated samples were more corrosion resistant than uncoated ASTM A-36 Steel specimens because of the corrosion potential (Ecorr) values of both coated samples were higher than uncoated ASTM A-36 Steel suggesting better anodic protection. The corrosion current density (Icorr) of both coated samples (Zn-Ni-Cu and Zn-Ni-Cu-TiB₂) were lower than uncoated ASTM A-36 Steel specimens also inferring better performance.Results of the current study concluded that Zn-Ni-Cu-TiB₂ coated ASTM A-36 Steel was able to enhance the microbial-induced corrosion resistance without deteriorating the microstructural, adhesion strength, and other properties of the coating. The mass loss for both Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ coatings was 88% less compared to uncoated ASTM A-36 Steel. It is seen from scanning electron micrographs that the coatings produced were well-developed with minimum pores and cracks. After immersion cycle tests none of the coatings showed delamination or microbial colony attachment to the surface compared to ASTM A-36 Steel wherein degradation of the whole surface is visible along with corrosion in the interface.