A new NDT technique based on bacterial cells to detect micro surface defects

• New NDT technique for micro surface defects based on the use of bacterial cells.
• Validation using Rhodococcus erythropolis cells in aluminum, steel and copper.
• Bacterial cells penetrate and adhere preferentially to surface defects.
• Bacteria grow inside defects, under carbon medium, allowing identification by naked eye.
• Defects with depth of 4.3, 2.9 and 6.8 µm were identified in Al, steel and Cu, respectively.

This paper presents a new NDT technique based on bacterial cell suspensions to identify surface micro defects in a procedure similar to the one used in dye penetrant. Validation was performed using Rhodococcus erythropolis bacteria in aluminum, steel and copper samples, studying the penetration, liquid removal and revelation stages and the phenomena involved in each one, as well as, bacteria/material interaction. A detectability limit was estimated and this was seen to depend on the material. Under the tested conditions defects with a depth of 4.3, 2.9 and 6.8 µm were identified in Al, steel and Cu, respectively.

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