As greater emphasis is placed on the development of small fuel-efficient cars, there is a growing need to reduce the size of the inverter used in hybrid vehicles (HVs). However, semiconductor devices and other components are generating larger amounts of heat and the parts used to cool these components are becoming thinner. One issue resulting from these trends is perforations that propagate from coolant paths. This development secured corrosion resistance by controlling sacrificial corrosion protection performance, optimizing the use of Mn and Si materials to reduce susceptibility to grain-boundary corrosion, and taking a microstructural approach to the flow of the brazing filler metal. The developed material was applied to the inverter cooler of a small HV released at the end of 2011.