Morphological Evaluation of a Multispecies Biofilm on A106 Gb Industry-finished Steel Used from Heat Exchangers

Abstract

Biofouling in heat exchangers is a challenge in industry leading to efficiency and maintenance losses. A 3.4 % of the global gross domestic product (GDP) in 2013, estimated the global cost of corrosion to be US$ 2.5 x 1012. The purpose of the study was to evaluate the stages of multispecies biofilm formation on finished steel surfaces with emphasis on bacterial cell attachment at early stages. Although many studies have been conducted regarding bacterial attachment to metallic surfaces, little is known about the impact of the conditions and mechanisms of attachment in the early stages. It is not known which type of bacterial strains will selectively attach in this environment. Third-generation sequencing was conducted to give insight on the abundant species at the surface, and it was observed that Firmicutes attached to the rough and smooth surfaces and Pseudomonas sp. was prevalent on the rough surfaces. Scanning electron microscopy (SEM) was used to count the abundant rod-shaped bacteria in colony sites on smooth surfaces on day 3 only. However, on rougher surfaces bacteria could not be easily detected due to biofilm fully covering the sites. Atomic Force Microscopy (AFM) was used to quantify surface roughness on the bacterial biofilm. Roughness values from the AFM on the smooth surface showed a significant increase as compared to the rough surface, indicating bacterial attachment. Mature and complex structures started forming at later growth stages. Smooth finished surfaces showed reduced biofilm formation and selective attachment of Pseudomonas sp. on rough surfaces is known to aid in steel corrosion and subsequent failures.