Study on Nontraditional Processing Utilizing Microbiogenic Functions

本研究的最终目的是开发利用微生物功能的非传统材料加工。作为第一步的目的，在海水中的微生物腐蚀的一般特性进行了实验研究，通过对各种金属的腐蚀试验，并从结果的一些微生物的处理进行了尝试。所得结果如下：I.微生物腐蚀的一般特征研究（1）试验结果表明，大量微生物在所有试验金属表面定向聚集，并附着在金属表面和腐蚀产物上。(2)阐明了微生物在无氧铜腐蚀中的作用：好氧菌促进了铜氧化物的水化;点蚀是硫酸盐还原菌等厌氧细菌作用的结果;氧浓差电池促进了点蚀的形成。(3)与无菌条件下的腐蚀相比，微生物更倾向于在镇静钢的晶内腐蚀到晶界，从而显著促进腐蚀。微生物加工的尝试（1）通过人工制造厌氧环境，提出了一种在厌氧细菌作用下在金属表面产生凹陷细节的方法，简称MBM凹陷工艺，并证明了该方法的有效性。(2)提出了一种利用缝隙腐蚀和微生物腐蚀共同作用在金属表面形成凸形细节的原理，即MBM凸形工艺。OFHC表面印有小字母，但目前还不令人满意。(3)提出了一种在生物处理过的基底上存款并生长金属晶体的方法，称为MBD法。这些结果在日本中小企业东海分支夏季会议（1992）上发表，并将在1993年三重市国际研讨会（IMM'93）上报告。

A final purpose of the present research is to develop nontraditional materials processing utilizing microbiogenic functions. As the first step for the purpose, general characteristics of microbial corrosion in the seawater were examined experimentally by the corrosion test for various metals, and from the results a few microbiogenic processings were attempted. Results obtained are as follows:I. Study on General Characteristics of Microbial Corrosion (1) It was confirmed that a number of microorganisms gathered orientatively to all the tested metals, and inhavited their surfaces and corrosion products. (2) Microbiological effects on the corrosion of oxygen-free high-purity copper (OFHC) were clarified; aerobic bacteria acted to promote hydration of Cu oxide; pits were caused by action of anaerobic bacteria such as sulfate-reducing bacteria (SRB); resultant oxygen concentration cells assisted their formation. (3) Microoganisms preferred to corrode in-grain to grain boundary in the case of killed steels, and thus promotes markedly corrosion, compared with corrosion under a sterile condition.II. Attempt of Microbiogenic Processing (1) A method to produce concave details on metal surface with the action of anaerobic bacterium, referred to as MBM concave process, was proposed by making artificial anaerobic environment, and was shown to be valid. (2) A principle to produce covex details on metal surface, referred to as MBM convex process, was attempted utilizing the combined action of crevice and microbial corrosions. Small letters were printed on the OFHC surface, although not satisfactory at present. (3) A process to make a metal crystal deposit and grow on the substrate, which was bioprocessed in advance, was presented, and called MBD process. Its validity was confermed by making copper crystals.These results were presented at The JSME Tokai Branch Summer Conference (1992), and are to be reported at the International Seminar (IMM'93 Mie) held in 1993.