My customer wants to use some galvanized supports for a furnace. The normal temperature around the steel will be about 475 degrees F. is this a good application for galvanized material?

The galvanized material will generally not work well at 475 degrees. The surface will peel leaving only a fraction of the original zinc on the surface. The Canadian government has conducted a considerable amount of research on the subject and has published a paper on high-temperature peeling of coatings. This would not be a good application for galvanizing