Letter Evaluation of microbiologically in¯uenced corrosion inhibition using electrochemical noise analysis A. Nagiub 1 , F. Mansfeld * Corrosion and Environmental Eects Laboratory CEEL), Department of Materials Science and Engineering, School of Engineering, University of Southern California, University Park, Los Angeles, CA 90089-0241, USA Received 12 March 2001; accepted 4 May 2001 Abstract Microbiologically in¯uenced corrosion inhibition MICI) has been observed for Al 2024, mild steel and cartridge brass when an arti®cial seawater AS) solution containing growth medium was contaminated by bacteria. Impedance data clearly showed that pitting did not occur under these circumstances for Al 2024. For mild steel corrosion rates were decreased signi®cantly. For brass corrosion rates were also greatly decreased and tarnishing was not observed. Analysis of electrochemical noise data obtained for the three materials in AS with and without growth medium did not reveal signi®cant changes due to MICI except for an increase of the noise resistance R n and a parallel shift of the current power spectral density plots to lower values for Al 2024 and mild steel. The observed increase of R n was mainly due to a signi®cant decrease of the standard deviation of the current ¯uctuations. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Aluminum; Mild steel; Brass; Microorganisms; MICI; Seawater; Electrochemical noise analysis 1. Introduction As discussed elsewhere [1], microbiologically in¯uenced corrosion inhibition MICI) has been observed for several materials due to contamination of an arti®cial www.elsevier.com/locate/corsci Corrosion Science 43 2001) 2001±2009 * Corresponding author. Tel.: +1-213-740-3016; fax: +1-213-740-7797. E-mail address: mansfeld@usc.edu F. Mansfeld). 1 Permanent address: Department of Chemistry, Faculty of Sciences, Al-Azhar University, Assuit, Egypt. 0010-938X/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0010-938X01)00079-8