Abstract
Bacteria having the ability to produce corrosive pits on metal surfaces were detected from Microbiologically Influenced Corrosion (MIC) failure case analysis. The target of this study is to apply the corrosive ability of these bacteria to material processing.
In previous reports, the authors focused on Staphylococcus sp. and its ability to corrode copper. Those studies showed the possibility of bio-etching with Staphylococcus sp. by defining the processing area with a protective resist.
In this report, another strategy of bio-etching is described, i.e., to define the processing area by controlling the phase of the material.
One of the characteristics of MIC is that in stainless steel welds the corrosive attacks occur preferentially on certain phases. Applying this phase-preferential corrosion property to material processing lead to the new method of bio-etching, namely, the location of the processing area can be defined by controlling the metal structure.
The following experiments were designed to verify this idea. Bacillus sp. and Pseudomonas sp. were selected as the test strains. The optimal bio-etching parameters, the adhesion area of the bacteria as well as the change of pH of the culture medium were evaluated. A processing bioreactor prototype was then designed based on these results. Finally an experiment for bio-etching of stainless steel welds was carried out.
This study confirmed that bio-etching process is suitable for position selective etching, by controlling the metallic phase of the material.
