Corrosion in refinery operations has been, and still is, the subject of many studies, papers, courses and web forums. Although a lot of what has been written shows that significant progress in understanding corrosion has been made, it also makes it clear that the problem continues to exist and that quite possibly is getting worse.
It is estimated that the global costs of refinery corrosion are in the order of 15B USD annually. Getting more exact numbers is not possible as refineries do not make available the extent of their corrosion problems, which is understandable considering the ever increasing environmental legislation they face. It is worth mentioning that in these costs, profit losses and loss of production uptime have not been taken into account. An analysis report by NACE International states that in the USA alone annual profit losses due to refinery corrosion may be as high as 12B USD!
Despite extensive research and vast amounts of available literature, many of the corrosion mechanisms are not yet fully understood. The problem with petroleum refining is that there is not one single source of corrosion, but many. To add to the problem, some of the corrodents might interact and increase or inhibit each other's corrosivity. Also, physical process conditions play a role; so temperature, flow and Reynolds number have to be taken into account too.