Mineral wool has been used for well over half a century as insulation to reduce heat loss, provide personnel protection, and protect against hearing loss. Corrosion under insulation (CUI) has been a major topic of interest as process facilities age and experience issues with corrosion, particularly on pipelines. Efforts have focused on reducing any effect of the insulation material on corrosion – e.g., by reducing chlorides, making the insulation hydrophobic, and recently, by upgrading the hydrophobic performance in terms of high-temperature resistance. The next step is to introduce a proprietary corrosion inhibitor within the mineral wool. If water does make its way to the metal substrate, the inhibitor will activate in contact with water to mitigate corrosion. This paper will present the CUI-mitigating efficacy of mineral wool with an integral corrosion inhibitor using the ASTM C1617 test modified for various chloride concentrations above the standard. The paper also discusses corrosion-inhibiting mechanisms, particularly how such mechanisms can modify the environment around steel substrates to mitigate factors that advance stress corrosion cracking.