海洋环境中芽孢杆菌对聚氨酯清漆涂层分解的影响

Effect of Bacillus flexus on Degradation of Polyurethane Varnish Coating in Marine Environment

采用电化学技术、扫描电镜和红外光谱等多种方法研究了海洋环境中芽孢杆菌对聚氨酯清漆涂层分解作用以及对腐蚀行为的影响。结果表明,在浸泡时间为1 h时,芽孢杆菌并没有对聚氨酯清漆涂层产生明显的降解作用。随着浸泡时间的延长,在含有芽孢杆菌的海水中的涂层耐蚀性明显小于在无菌海水中涂层的耐蚀性,表明芽孢杆菌能导致涂层的降解。浸泡初期,在无菌海水和芽孢杆菌海水中,涂层电阻值约为10^(8)Ω·cm^(2)。经无菌海水浸泡13 d后,涂层电阻值下降为5.22×10^(6)Ω·cm^(2),浸泡第35 d时,涂层电阻值变为5.46×10^(6)Ω·cm^(2)。而经芽孢杆菌海水浸泡样品的涂层电阻值在浸泡13和35 d后分别为2.16×10^(6)和7.96×10^(5)Ω·cm^(2)。芽孢杆菌海水浸泡涂层电阻值的减小量明显大于无菌海水浸泡涂层电阻值的减小量。扫描电镜的结果显示,在浸泡35 d后,在芽孢杆菌海水溶液中浸泡的涂层出现大量孔洞和粉化痕迹。由红外光谱结果可以观察到,浸泡在芽孢杆菌海水的N—H键和C—O键吸收峰比无菌海水中浸泡涂层低,说明芽孢杆菌可分解涂层。

The effect of Bacillus flexus on degradation and corrosion behavior of polyurethane varnish coating in marine environment was investigated by means of electrochemical impedance spectroscopy(EIS),scanning electron microscope(SEM)and Fourier transform infrared spectroscopy(FTIR).The results showed that the Bacillus flexus did not exhibit significant effect on the degradation of the polyurethane varnish coating after immersion in Bacillus flexus containing seawater for 1 h.With the extension of immersion time,the corrosion resistance of the coating was significantly lower in Bacillus flexus containing seawater than that in sterile seawater,indicating that Bacillus flexus could cause the degradation of the coating.The coating resistance was about 10^(8)Ω·cm^(2)at the initial stage of immersion both in sterile seawater and Bacillus flexus containing seawater.However,the corrosion resistance of the coating dropped to 5.22×10^(6)and 5.46×10^(6)Ω·cm^(2)after immersion in sterile seawater for 13 and 35 d respectively.As comparison,the corrosion resistance of the coating decreased to 2.16×10^(6)and 7.96×10^(5)Ω·cm^(2)after immersion in Bacillus flexus containing seawater for 13 and 35 d,respectively.The facts showed that the corrosion resistance of the coating in Bacillus flexus containing seawater decreased larger than that in sterile seawater.SEM observation result showed that after immersion for 35 d in Bacillus flexus inoculated seawater,numerous pores and pulverization signs could be observed of the coating surface.From the result of FTIR,the absorption peaks of N—H bond and C—O bond of coatings after immersion in Bacillus flexus containing seawater were significantly lower than that in sterile seawater,indicating that Bacillus flexus can clearly degrade the polyurethane varnish coating.