Polymeric materials, particularly fiber reinforced composites (FRPCs) are strategically important to the Air Force. We have shown that common fungi form biofilms on five types of FRPCs. Our data indicate that the fungi penetrate the material. They utilize the resins and sizing chemicals as energy and carbon sources. We used electrochemical impedence spectroscopy (ElS) to investigate degradation of the FRPCs. We demonstrated a progressive decline in impedence in 179 days as a result of fungal growth on the FRPCs. Our data indicate that the composite materials are susceptible to microbial attack in moist conditions at ambient temperatures. We also investigated the effects of chromium, used in surface coatings, on microbial activity. Initial tests showed that both hexavalent and trivalent chromium inhibits bacterial activity. However, the bacteria rapidly develop resistance to chromium.