A new, environmentally friendly coating that protects metals against corrosion in seawater has been developed by a team of researchers from Sheffield Hallam University. At the Society for General Microbiology meeting in Harrogate today, Jeanette Gittens and colleagues described how they had encapsulated spores from a bacterium into a sol-gel coating which then protected an aluminium alloy from microbial corrosion.
Microbially-influenced corrosion (MIC) of metals at sea is a big safety and financial problem caused by the production of damaging substances such as hydrogen sulphide by sulphate-reducing micro-organisms within biofilms on the surfaces. Overall it is estimated that corrosion costs the UK around 3-4% of GDP. Existing anti-corrosion treatments are costly, ineffective and often include biocides and inhibitors that are toxic to aquatic life.
The corrosion-preventing bacteria occur naturally in the environment. Incorporating its spores into the coating did not seem to affect their viability - living cells were still found in the coating after more than six weeks in seawater. The coating could also be heat cured at temperatures up to 90°C.
Speaking at the meeting, Ms Gittens said, "Our results from laboratory studies and a field trial in the Thames estuary have shown that the bacteria-containing coating is substantially more effective in the prevention of corrosion than the sol-only coating. We are investigating what causes the corrosion protection - we think it might be due to the immobilized bacteria producing antimicrobial agents which inhibit the growth of corrosion-causing microorganisms". Additional trials are now planned or in progress in a variety of marine environments.