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Electrochemical impedance study on the formation of biological iron phosphate layers

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Author: Breur, H.J.A. · Wit, J.H.W. de · Turnhout, J. van · Ferrari, G.M.
Type:article
Date:2002
Institution: TNO Industrie
Source:Electrochimica Acta, 13-14, 47, 2289-2295
Identifier: 236553
doi: doi:10.1016/S0013-4686(02)00096-8
Keywords: Bacteria · Bioprotection · Corrosion protection · EIS · Phosphating · Pseudomonas putida · Adsorption · Bacteria · Corrosion protection · Electric impedance · Heavy metals · Iron compounds · Phosphates · Phosphoric acid · Spectroscopy · Bioprotection · Electrochemistry

Abstract

Phosphating is the most commonly applied pre-treatment process. However, some disadvantages exist: heavy metals and phosphoric acid are used in the process. Volkland et al. developed a process, in which these compounds can be left out, using bacteria to activate the phosphating process. This paper addresses the analysis of this phosphating process using electrochemical impedance spectroscopy. EIS-measurements are carried out during 150 h to understand the electrochemical processes taking place during the phosphate formation. A model is derived that can explain the processes. The process appears to be a two-step adsorption process. The first step is formation of a thin layer of bacterial products. Formation of a dense layer of iron phosphates as a second step takes place within 2 days. © 2002 Elsevier Science Ltd. All rights reserved.