<p>The global shift toward carbon capture and storage (CCS) and hydrogen energy has intensified interest in hybrid CO₂–H₂ pipeline systems, where both gases are transported at high pressures through shared infrastructure. While economically attractive by reducing the need for two separate pipelines and potentially lowering environmental impacts through minimized construction work, such systems face unique challenges related to failure mechanisms and corrosion behavior that are not yet fully understood. CO₂ transport is prone to carbonic acid corrosion and localized attack under wet conditions, whereas hydrogen exposure introduces embrittlement, blistering, and cracking. When combined, these gases create synergistic effects that accelerate material degradation, compromise weld integrity, and increase the risk of catastrophic failure. This paper provides a comprehensive analysis of metallurgical failure mechanisms in hybrid CO₂–H₂ pipelines, identifying key risk factors such as operating pressure, gas impurities, temperature, and materials selection. Mitigation strategies are reviewed, including corrosion-resistant alloys, protective coatings, operational controls, and real-time digital monitoring. Case studies and ongoing research projects are discussed to highlight practical lessons and remaining knowledge gaps. By integrating materials and corrosion science with mechanical engineering, this study outlines a roadmap for safer and more reliable hybrid pipeline transport. The findings emphasize the urgent need for standardized testing and design guidelines as hybrid pipeline deployment expands worldwide.</p>