The efficiency of upgrades such as process improvements are constantly considered in chemical plants. However the construction materials of plant equipment remain from the original process design. Chemical process modifications cause change in the composition of the service environment. This may affect the degradation of the construction materials. It is very difficult to predict the degradation of materials before design changes that influence of the service environment not only because of the process change but also because of modifications to the equipment configuration. This paper describes a case study of the investigation of corrosion damage to plant equipment that resulted from a process change and the use of advanced corrosion monitoring instrumentation to develop countermeasures that enabled the process change to be implemented satisfactorily.