The chemistry of materials plays an important role in ensuring that they are fit for their design purpose and perform adequately in service. The chemistry of process fluids which these materials encounter during operations is also a key determinant of the severity of degradation the materials will experience. Here, we elucidate how these two aspects of chemistry affect materials performance and asset integrity during high temperature exposure (> 450oC). We clarify, through case studies, the fundamental chemistry driving the degradation, and show how precise alterations in chemistry can constitute engineered mitigations to such in-service integrity issues.