Effects Of Pseudomonas On The Deteriorotion And Corrosion Protection Performance Of Polysiloxane Coating In Sea Water

Seawater is a highly corrosive media.In recent years,with the development and utilization of marine resources getting more in-depth,the protection of ships and other ocean facilities was become increasingly important.In the tropical marine environment,there were a lot of microbes.In order to reduce the corrosion of variety marine facilities,people use organic coatings on the metal surface to protect substrates.The direct contact between marine facilities and seawater was organic coatings.Thus,the microbes in seawater can effect on the organic coatings directly.Polysiloxane coatings can reduce bio-fouling by reducing the surface energy of a structure.There had been a lot of research reports on the influence of microbial on metal corrosion.However,the impact of microbial decomposition of the coatings and the etching processes are rarely reported.In this work,in order to understand the effects of Pseudomonas on the deterioration of a polysiloxane coating in seawater,we carried out a systematic comparison of the deterioration of the coating in sterile seawater and seawater inoculated with Pseudomonas.First,the electrochemical behavior of the coating in both kinds of seawater was examined by electrochemical impedance spectroscopy(EIS),and an equivalent electrical circuit(EEC)model was proposed to interpret the electrochemical impedance data.Second,the morphology of the immersed coatings was investigated by scanning electron microscopy(SEM).Finally,the breakdown of the chemical structure of the immersed coatings was evaluated by Fourier transform infrared spectroscopy(FTIR).The Nyquist plots of three coatings immersed in two different electrolyte solution’s each time points shows that there was a single time constant obtained at every immersion time and only one EEC obtained for both seawater systems revealed that Pseudomonas only slightly decomposed the coating.The occurrence of only one time constant at every immersion time indicated that Pseudomonas did not form a mature biofilm on the coating surface and that the under-coating corrosion did not occur extensively,which suggested that the polysiloxane coating had good anti-fouling performance and anti-corrosive properties because of its low surface energy.Thus,Pseudomons only slightly broke down the coating.For three coatings,the degree of decrease in the capacitive loop diameter observed from 3 d,5 d to 13 d of immersion was significantly higher in the seawater inoculated with pseudomonas than in sterile seawater.With the increase of the water contact angles of the coatings,the coating resistance decreased more slowly.The SEM and FTIR results verified a certain extent of degradation of the 30 d immersion coating by Pseudomonas.Nevertheless,the very slight influence of Pseudomonas on the capacitive loop diameter and the resistance of the coating suggested that Pseudomonas had only a small effect on the corrosion resistance of the coating over a long period of immersion.