4.2. ERMUSR 05-12-2009 - Laserfiche WebLink

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~'°chnicau ~$te.aet3te l~i~. 95-~0 '{°a~ Cohesive Stress Factor: Cohesive stress factors for various generic type coatings on a scale of 1 (low) to 5 (high) can be found in Table 2, rage 5. System Selection vs. itisic c& Stress Factors: Based on the fact that cohesive stress exerted by an overcoat system is directly related to the delamination potential of an existing paint system, Table 3 and Table 4 on page ti can be used as guides in selecting candidate Tnemec overcoat systems. Table 4 contains a partial list of overcoat systems available from Tnemec. i'.andirlate Svstem(s) Test Patches: Before making the firai decision on whether or nor to suggest a specific overcoat system, it is important to evaluate the adhesion of the candidate overcoat system(s) to the existing paint system. Make sure the existing system is dry and clean prior to applying test patches. Use ASTM D 5064 Standard Practice for Conducting a Patch Test to Assess Coating Compatability as a guide in conducting adhesion test patches. Use ASTM D 3359 Method A to evaluate adhesion of the new system ±o the old. The overcoat system should not wrinkle, lift or show any other adverse effects to the existing system. The adhesion of the existing system should be at least as good to the substrate and between coats as originally tested. The adhesion of the overcoat system to the existing system should exhibit an average adhesion rating of at least ~.0. Surface Prepaaation: Requirements may vary from job to job. A11 existing paint systems must be dry and clean prior to overcoating. This can usually be accomplished by power washing with 140° F. biodegradable detergent/water solution (l to Z oz. detergent per gallon of water) at 1000 to 2000 PSi at the rotating nozzle using 3 to 5 gpm delivery. Rinse with clean tap water. Some existing paint systems (e.g. two-component aliphatic polyurethanes) may require scarification prior to overcoating. If mildew is present, allow the surface to dry following the above power washing procedures. Wet mildewed surfaces with a bleach solution consisting of 3 parts warm water and 1 part household bleach. Allow the bleach solution to remain on the surface until dry. It will evaporate over a short period of time. Rinse with clean tap water. Rusty areas should be power tool cleaned (SP11 is the preferred method), and spot primed (Federal and local laws pertaining to the removal of lead-containing coatings will need to be considered). Edges of existing coating should be feathered to form a smooth transition prior to spot priming. Page 4 of E