This report documents the results of the July 1985 and July 1986 surveys of mirror module corrosion and torque tube damage at the 10 MW/sub e/ Solar Thermal Central Receiver Pilot Plant. It also assesses the effect of vent tubes on the corrosion growth rate. Results show that 0.052% and 0.061% of the total reflective area of the heliostat field was corroded in 1985 and 1986, respectively. However, the corrosion growth rate is much less than in previous years, primarily because of the effect of mirror module vent tubes. In the July 1984 survey, 35 torque tubes were damaged due to impact with the gear box. The 1985 survey showed that 14 of those same torque tubes were re-damaged. In addition, 9 newly dented ones were found. In the July 1986 survey, 39 torque tubes were dented, of which 4 were redented from 1985. The denting is caused when the gear-drive travels past the limit switch due to a shorted diode in parallel with the limit switch.