Effect Of Composite Bacteria On Microbial Corrosion Of Marine Engineering Materials

With the shortage of land resources,people gradually turn their gaze to the ocean which contains rich mineral resources.And the usage of ships,ocean engineering platform,submarine oil pipelines and other facilities and structures in the ocean engineering is increasing.In the marine environment,biology and microbiology attach to marine engineering facilities so that the service life of the facilities inevitably reduces.Especially,the loss of the marine engineering facilities caused by microbial corrosion is very serious.And in our country,many hidden dangers are existed in the operation of the marine engineering facilities.Therefore,the basic theory of corrosion protection for marine engineering materials is established,which provides theoretical support for the design,construction and material selection of marine engineering facilities.And it has very important practical significance to improve the design ability and the construction level of the marine engineering in our country.In this paper,electrochemical experiments and corrosion morphology observation were used to study the corrosion behaviors of the main materials in marine engineering facilities of brass and low-carbon steel in the conditions of five kinds of different environmental media of Sulfate-reducing bacteria,Pseudomonas aeruginosa,Alcaligenes sp and its complex strains.The experimental results show that the brass can accelerate corrosion by cathodic depolarization under the condition of single Sulfate-reducing bacteria.With the increase of immersion time,the negative shift of corrosion potential and the positive shift of the corrosion current density indicate that the corrosion is more severe.In Pseudomonas aeruginosa,the formation of microbial film for the brass plays a certain role in corrosion inhibition in the early stage.But with the soaking time,the corrosion inhibition effect weaken or even promotes the process of corrosion.The Q235 lowcarbon steel can accelerate corrosion by cathodic depolarization under the condition of single SRB solution.A large range of localized corrosion occurs on the surface of the sample.In the Alcaligenes sp solution,the corrosion rate of the mild steel is accelerated due to the difference of the oxygen concentration at the initial stage.Corrosion reaction slows down later while the corrosion of the sample surface is relatively light.Brass in solution which contains compound bacteria of SRB and P.Aeruginosa,its corrosion current density is between that in single P.Aeruginosa and that in SRB.The corrosion current density of Q235 mild steel in the mixed solution which includes SRB and P.Aeruginosa is less than that in the two kinds of single bacteria.The corrosion current density of Q235 in the mixed solution which includes SRB and Alcaligenes sp is similar to that in the single Alcaligenes sp.In conclusion,both the Pseudomonas aeruginosa and the Alcaligenes sp have inhibitory effect on the growth of Sulfate-reducing bacteria.