The Time to First Maintenance (TFM) Chart was developed from real world data and a corrosion prediction model, the Zinc Coating Life Predictor (ZCLP). The corrosion rate data was collected from galvanized steel samples exposed to the five defined environments in locations around the world and then coupled with the statistical methods and neural network technology of the ZCLP.

The data points of the TFM chart are based on macroscopic environmental data and, thus, may vary from the actual corrosion rate observed, due to site-specific environmental conditions. Atmospheric levels of airborne salinity, precipitation, relative humidity, sulfur dioxide, and temperature influence actual corrosion rates in a specific geographic location. Zinc coating thickness is linearly related (on a macrolevel) to the time to first maintenance of hot-dip galvanized steel.

Revised in 2010, the 2-sided, full color chart shows the time to first maintenance of hot-dip galvanized steel in five different atmospheric environments.  The reverse page contains a singled-out view of the industrial environment's time to first maintenance.