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Graphene is an attractive 2D coating material because its remarkable physico-chemical properties enable numerous applications. Graphene coating was deposited on Monel 400 alloy by chemical vapour deposition (CVD) for corrosion resistance in a marine environment containing sulphate reducing bacteria (SRB). Surface morphology and coating characterization were performed using scanning electron microscopy (SEM) and Raman spectroscopy. Electrochemical results revealed that the multilayer graphene coating that replaced the native protective oxide layer on the Monel 400 surface provided superior corrosion resistance in the abiotic and biotic solutions. Post corrosion characterisation, using SEM and FTIR, supported the electrochemical findings.

The role of microbiological environments containing pure and mixed cultures of sulfate-reducing bacteria in stress corrosion cracking of carbon steel in biotic and abiotic environments was investigated. Carbon steel specimens were subjected to slow strain rate testing in a synthetic seawater environment (3.5% sodium chloride solution), with and without the microbiological cultures. Specimens tested in biotic (microbiological) conditions showed a considerable loss of ductility, as compared to those tested in abiotic conditions. Fractography of the specimens tested in abiotic solutions suggested features of only ductile failure (dimples), whereas those tested in biotic conditions had additional features of brittle cracking. Results also suggested the role of sulfate-reducing bacteria in promoting hydrogen-assisted cracking.

The paper presents results of a laboratory investigation of the microbiological environment assisted stress corrosion cracking of carbon steel in chloride solutions. Carbon steel specimens were subjected to slow strain rate testing (SSRT) in an aqueous solution of 3·5% sodium chloride, with and without a microbiological culture. Specimens tested in the biotic (microbiological) conditions showed a considerable loss of ductility, as compared to those tested in abiotic conditions. Fractography of the specimens tested in abiotic solutions suggested features of only ductile failure (dimples), whereas those tested in biotic conditions also had features of brittle cracking. Results of SSRT tests of the specimens pre-subjected to the electrochemical conditions for hydrogen charging have indicated susceptibility of the steel to hydrogen assisted cracking, and therefore suggesting a role of microbial environment in promoting hydrogen assisted cracking.

Culicinomyces clavisporus, a fungal pathogen of a wide range of mosquito species, was investigated in relation to potential pathogenicity against Culicoides nubeculosus biting midge larvae. Seven different C. clavisporus strains were assayed. Each showed some degree of activity against C. nubeculosus larvae with LC50 values of between 3.2×10−5 and 1.1×10−6 spores/mL; these effects occurred in dose-dependent manners and tended to be delayed until 72–96 h post treatment. The results are discussed in relation to incorporation of C. clavisporus into biocontrol programmes for Culicoides spp.

The mosquito fungal pathogen Culicinomyces clavisporus was found to be sensitive to the antibiotics hygromycin B and phleomycin but resistant to kanamycin and geneticin. Protoplasts were genetically transformed to give strains resistant to phleomycin and hygromycin B. The results show that multiple integrations of transforming DNA can occur and that heterologous fungal gene expression signals are functional in C. clavisporus .