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FM <br />April 17, 1984 <br />Page No. 2 <br />Ninety-five percent of the pop -offs we see on these water towers <br />are on the lower bowl areas. We know that on warm, humid days <br />condensation collects on the outside tank surface. This wet/dry <br />condition over several months of the year, along with a hot/cold <br />climate of the area, tend to leach out the flexibilizers in the <br />coating. When this happens, the coating becomes harder and more <br />brittle. In turn, the film gets stronger along the horizontal <br />plane. Cold temperatures are introduced and the paint separates <br />from the substrate. It will break on the paint's weakest bond. <br />Whether the paint shrinks slightly, or the steel tank, or both, I <br />do not know. One thing we do know, cold weather is the catalyst <br />for the phenomena. <br />In ninety percent of the pop -off problems we see, a simple touch- <br />up was all that was used to correct the problem. our weather in <br />December was every bit as cold this year as it was in January of <br />1981. If we were to have a continuing problem on the tanks that <br />gave us problems in '81, we would have known it by now. We feel <br />for the most part once a tank pops paint at 70 degrees below, the <br />process will not repeat itself, at least to any great extent. <br />Since we have had every generic type of coating "pop -off", we see <br />no correlation between the type of coating and the problem. Also, <br />all manufacturers have had this problem, as well as painting <br />contractors. <br />if all repainted elevated water towers with 10 dry mils popped <br />paint at JO - 40 degrees below, the answer to this problem would <br />be simple. The facts are that less than five percent of them <br />ever have a problem. This number will shrink even more in the <br />future since we are recommending the use of thin film finish <br />coatings, such as Tnemec Endura-Shield. <br />I guess the bottom line is that we probably should alert a <br />customer that insists on brightening up an existing coating that <br />this can happen, especially if there is already 10 dry mils of <br />existing coating on the surface. <br />Sincerely, <br />Von Kling <br />Kling S Associates, Inc. <br />VK:g <br />1� <br />ATTACHMENT N1 - PAGE 2 <br />