4.2. ERMUSR 05-12-2009 - Laserfiche WebLink

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1?'esllnisal ~u9letin i~io. 9$-1® IZfl duly 2002 Adhesion/Film [ntegritya Before determining if the existing paint system is a candidate for overcoating, it is also important to obtain answers to the following questions: 1. What is the total film thickness? 2. How many coats of paint? 3. How good is the adhesion to the substrate and betvreen coats? 4. Are there f•.!m defects such as cracking or blistering? Physical and visual tests are required to answer the above questions and determine film integrity (cvercoating risk factors). Conduct the following tests at a minimum of 3 locations (3 trials at each location) and record results on attached Form No. l01 X 588. Draw a diagram of the structure on a separate piece of paper and mark the locations where tests were conducted. Large structures such as bridges should be divided into zones and a minimum of 3 locations tested within each zone. Use a separate Form No. 101 X 588 for recording test results at each zone. I . Measure total dry film thickness with a Tooke gauge, magnetic pull-off or magnetic flux film thickness gauge. Measurements should be taken at a minimum of ~ separate locations (3 trials at each location). 2. Determine approximate number of coats with a Tooke gauge or visual examination of a paint chip cross section. 3. Visually inspect the film far defects such as delamination, cracking and blistering. List any significant film defects that are observed. Existing coatings with extensive delamination or cracking should not be overcoated. If blisters are present, report blister size and frequency in accordance with ASTM D 7l4 Evaluating Degree of Blistering of Paints. (Existing systems that have extensive blistering should not be overcoated unless frequency of blisters is such that each blister or blistered area can be spot repaired.) 4. Check adhesion at the same locations (3 trials at each location) where dry film thickness readings were taken. Use the following adhesion test methods: "X" Scribe and Tape Test -Conduct this test in accordance with ASTIVi D 3359 Standard Test Methods for Measuring Adhesion by Tape Test, Method A. Adhesion is rated on a scale of 0 to 5 as outlined in the ASTM Test Method. No removal is rated as SA and removal beyond the area of the "X" is rated as OA. Knife Adhesion -Probe at the coating with the point of a knife blade in an attempt to delaminate the coating system between coats or from the substrate. Rate "knife adhesion" as poor, fair, good or excellent. Note: The ASTM D 3359 "X" scribe and tape adhesion test can sometimes give misleading results if only delamination around the "X" scribe is evaluated. Always examine the back (sticky side) of the tape. If it is covered with a thin layer of topcoat, rate the adhesion as "OA" even though the "X" scribe indicates better adhesion. Aged leafing aluminum coatings sometimes display this topcoat splitting phenomenon. Page 2 of 6