This paper reports an investigation of fatigue phenomena in Weir’s GEHO fluid end pump components, made of carbon steel materials exposed to corrosive environments and subjected to cyclic stresses. The research involved the development of a numerical simulation framework built to model corrosion fatigue mechanisms, supported by advanced crack growth simulations. Validation of the methodology was achieved through simulations of plane uniaxial specimens, U-shaped notched specimens, and lab-scale pressure component, showing a high degree of correlation between predicted and experimental results—both in terms of crack propagation paths (striation patterns) and fatigue life (number of cycles). Following this robust validation, the framework was applied to simulate crack growth and assess the fatigue lifetime of a positive displacement pump diaphragm housing component. The nCode software was used to identify critical locations, or hot spots, where initiation is most likely to occur. Subsequently, MSC Marc/Mentat was employed to perform advanced simulations of crack propagation under complex loading conditions. In addition to identifying critical points, an analysis of the crack growth orientation influenced by applied cyclic loading was also conducted. This application demonstrates the potential to accurately predict corrosion fatigue performance in complex real-world geometries, reducing the need for costly full-scale experimental testing. The findings provide practical insights into the durability and reliability of carbon steel parts operating under cyclic loading conditions in corrosive environments. The results have broader implications, offering valuable guidance not only for the design and maintenance of mineral processing pump components but also for a wide range of industrial sectors, including power generation and marine engineering.