Biocorrosion

Corrosion, which leads to changes in the mechanical properties of a material, is detrimental to the strength of metal structures, which deteriorate. All industrial sectors are more or less confronted with this problem. Corrosion phenomena have been widely studied for several centuries, due to the high cost of maintenance, the unavailability of installations and the risks to the safety of goods and people. As for the influence of micro-organisms on the evolution of corrosion, this has only been mentioned in French literature since the 1980s. Chantereau defines it as follows: "Bacterial corrosion encompasses all corrosion phenomena in which bacteria act directly, or via their metabolism, playing a primordial role, either by accelerating an already established process, or by creating conditions favorable to its establishment". More recently, French (NF) and international (ISO) standards (NF EN ISO 8044) define microbial corrosion as "corrosion associated with the action of micro-organisms present in the corrosion system" and bacterial corrosion as "corrosion associated with the action of bacteria".

To express this effect of bacteria on the corrosion of materials, several names are used. Some use the term CIM: corrosion influenced by micro-organisms, a translation of MIC: microbially induced corrosion. For simplicity's sake, the term "biodeterioration" is proposed to generalize the action of micro-organisms on all types of materials, whether metallic, mineral or organic. In this document, only metallic materials will be considered, which is why the term "biocorrosion" will be used, as is customary for these conditions.

It's also important to point out that the action of bacteria doesn't lead to a new form of corrosion, but causes a change in the kinetics of corrosion reactions, where it promotes a type of corrosion that, in the absence of bacteria, would have no reason to occur.

One of the reasons why the study of the action of micro-organisms on corrosion is so difficult to develop is partly due to the fact that this is a multi-disciplinary field par excellence. Microbiology studies the living world – microorganisms – and corrosion is concerned with inert elements: materials. However, one scientific specialty unites them: electrochemistry in the aqueous domain. Unfortunately, the vocabulary used by specialists in these two disciplines is not always identical to express the same concept. That's why we've provided translations of some of the terms commonly used in the two disciplines.

Water is essential for the development of micro-organisms (without it, they can only survive in a dormant state) and for aqueous corrosion. Another very important element is oxygen.