Flow sensors having nanoscale coating for corrosion resistance

A corrosion resistant flow sensor apparatus includes a flow sensor including a micromachinable substrate mounted on a package substrate that includes electrically conductive traces and substrate bond pads. The flow sensor includes a MEMS sensing structure for sensing a mass flow parameter and sensor bond pads coupled to the sensing structure. The sensor bond pads include a top metal layer on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall. Bond wires couple the sensor bond pads to the substrate bond pads. A housing including sides and a top portion is around the flow sensor and includes a flow channel having an inlet and an outlet. A multi-layer corrosion protection coating includes a nm scale adhesion layer and a self assembled monolayer (SAM) is on the adhesion layer. The protection coating covers the sensor bond pads including the metal diffusion barrier layer sidewall.