We investigate the polarimetric scattering properties of highly absorbing and highly reflective rough surfaces in the IR. We obtain Mueller matrix measurements from these surfaces and compare the data to a Fresnel model. From the data, we determine that a rough, highly absorbing surface has a higher degree of polarization compared to a rough, highly reflective surface. In addition, we present a full polarimetric version of the microfacet model and discuss its properties. This closed-form result for the polarimetric bidirectional reflectance distribution function (BRDF) is derived from the microfacet model.