Zinc Coating Life Predictor
The Zinc Coating Life Predictor, new software which was developed by Gregory Zhang of Teck Cominco Metals Ltd., has led to a new way to estimate the corrosion rate of zinc in various environments. The program performs calculations based on models that were developed using statistical methods, neural network technology and an extensive worldwide corrosion database. The environmental data input required to estimate a corrosion rate includes temperature, airborne salinity, sulfur dioxide concentration, relative humidity, rainfall, and sheltering condition (indoor, rain-sheltered, or outdoor). Once these values are known, the software calculates and reports a corrosion rate and also gives the option to either calculate the predicted life, given the coating thickness, or the coating thickness required to achieve a specified life. This software was used to develop an anticipated service life of hot-dip galvanized steel of varying coating thicknesses in a wide array of environments.
The environmental data required to use the Zinc Coating Life Predictor was obtained from resources on the World Wide Web. All of the predictions made were assumed to be in open atmosphere and subject to all environmental conditions. The temperatures and annual precipitation (or rainfall) were gathered from www.weather.com, which is the Weather Channel's site. The relative humidity data was also gathered via the Internet from the National Weather Service (www.nws.mbay.net/rh.html), which had annual relative humidity data for numerous cities throughout the U.S. The sulfur dioxide concentrations were determined from a report produced by EPA that lists the peak air quality statistics for the major pollutants. This file can be found online at www.epa.gov/oar/aqtrnd00/pdffiles/factbook.pdf. Some cities, particularly rural, do not monitor their levels of sulfur dioxide due to their low concentration. These values were estimated to be the lowest of all the concentrations. Air salinity data for numerous environments does not readily exist. Some data exists for areas close to the sea; therefore, for inland areas, these values were estimated based on their distance from the ocean and from any other known data. Some examples of airborne salinity data can be found on the Zinc Coating Life Predictor Web site, as can examples of the other four environmental parameters.