Metallurgical Evaluation of Corroded Paper Processing Equipment, 2010 TAPPI PEERS Conference

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Corrosion causes substantial damage to the equipment used to process and manufacture paper. Many of the process steps used to produce paper products have environments that can be corrosive to the process equipment. Although the original equipment manufacturers design and select materials that are typically appropriate for the application, there are many instances when significant corrosion occurs and components are damaged. This results in substantial cost for downtime and replacement of the component. In some cases the repaired component does not perform as well as the original equipment. The most economical approach is to avoid the corrosion in the first place. In many cases corrosion cannot be avoided, but it can be mitigated. The corrosion can be reduced if there is a proper understanding of the type of corrosion that has occurred or is expected to occur. Therefore, when corrosion is present it is important to examine the component to determine how the corrosion developed. Was it due to uniform corrosion, pitting corrosion, stress corrosion cracking, microbiological influenced corrosion or some other reason? Did the corrosion develop due to improper selection of steel, defects in the material or incorrect processing of the steel? In some cases, manufacturing processes such as weld fabrication may result in reduced corrosion resistance in the heat affected zone or weld deposit. Improper or inadequate subsequent removal of the heat tint and passivation of the damaged region can result in pitting corrosion of stainless steels. It is essential that the components be thoroughly examined to determine how the corrosion developed, if the reason why is to be defined. This can be done by conducting a metallurgical evaluation of representative corroded material.