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, (Monday 30 March), 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.