Corrosion as a major hazard concern for the petroleum refinery industry

Corrosion does not stand for a single phenomenon but is a generalized term to cover a destructive attack on a metal as a result of either a chemical or electrochemical reaction between the metal and various elements present in the environment. 

For instance, iron is converted into various oxides or hydroxides when reacting with the oxygen present in air/water, when in contact with a more noble metal such as tin or when exposed to certain bacteria.  The international standard defines corrosion more specifically as a “physicochemical interaction between a metal and its environment which results in changes of the properties of the metal and which may often lead to impairment of the function of the metal, the environment, or the technical system of which these form a part.” According to other authors, corrosion derives from “the natural tendency of materials to return to their most thermo dynamically stable state.” 

Table 3 below identifies four broad categories of refinery elements that can contribute to corrosion risk.

Corrosion of a metal occurs either by the action of specific substances or by the conjoint action of specific substances and mechanical stresses.  Depending corrosion (e.g., galvanic corrosion, pitting corrosion, hydrogen embrittlement, stress sulphide corrosion cracking) are characterized by the type of mechanical force to which the metal component is exposed.  It is not within the scope of this work to address in depth either corrosion electrochemistry or the identification of different forms of corrosion. 

The basics of corrosion mechanisms are described as a basis for understanding the conditions that make corrosion risks highly relevant for refinery operations and more specifically to provide some insight into the underlying causes of the corrosion events leading to the accidents analysed in this report.  Also, corrosion of certain metals (e.g. aluminium) enhances their corrosion resistance, but in this work corrosion is assumed to be solely an undesirable phenomenon.

Source:https://ec.europa.eu/jrc/sites/default/files/lbna26331enn.pdf