September 7 - September 12, 2010
What kind of coating system, including surface preparation, should be used to protect a steel factory roof that is subject to hydrochloric acid vapors and other industrial pollutants and particulates in a hot, humid environment?
Jorge Lizarraga of International Paint on
September 20, 2010:
In my opinion, the ideal coating to use in this service is a vinyl ester novolac coating, or a glass flake reinforced vinyl ester. The primer should be 2 to 5 mils thick, and the
finish coat should be 15 to 25 mils thick.
Surface preparation should be SSPC-SP 10.
Nowadays, these sorts of coatings are used to succesfully paint tanks containing hydrochloric and sulfuric acid.
Marco Antonio Alvarado Meneses of Sherwin Williams Perú on
September 9, 2010:
It is important to see that there is no single coating or coating system that can satisfy every service condition or environment that exists. Selecting the best coating system for a given exposure environment is dependent on identifying and understanding how the particular environment impacts various coatings.
Often, the coatings selection is based on knowledge of other (similar) processes or projects. Sometimes the effects of certain chemicals and conditions on various generic types of coatings are not known. It is advisable to carry out testing in order to verify a good performance of the selected coating. Testing should be based on the environment to which the coating will be exposed
In addition, the coating choice or paint operation may be restricted by environmental regulations and other constraints. Most coating manufacturers provide information on the resistances and application tolerances of their products.
The following criteria should be considered prior to system selection:
Type of structures to be coated Identify exposure environments Identify regulatory requirements
Select coating materials for project
Identify surface preparation and application requirements
The more aggressive the environment, the higher performing the coating and surface preparation system should be.
Rudi Rennert of Rhino Linings Corporation on
September 7, 2010:
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First, the in-service solution strength, additional chemical exposures, and environmental temperatures should be considered before specifying a particular coating. Once an appropriate coating has been chosen on the basis of having complete information, then the preparation can begin.
The steel roof should be abrasive-blasted to a near white finish (SSPC-SP 10). Chloride testing should be done to insure no soluable salts remain on the surface. A zinc-rich epoxy primer should be applied to the chloride- free, clean, dry surface. Finally, a coat of a highly crosslinked, chemically resistant polyurethane/urea should be applied to 60-80 mils.
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