Protective barriers for small devices, such as sensors, actuators, flow control devices, among others, protect the devices from erosive and/or corrosive fluids, for example, formation fluids under harsh downhole conditions. The protective barriers include protective coatings and fluid diverting structures in the fluid flow which facilitate use of the small devices in high temperature-high pressure applications with erosive and/or corrosive fluids that are often found in downhole environments.