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standard show that tests conducted us ing the pneumat ic equipment (Method D) and the hydraulic equip- ment (Methods C, E, and F) consistently achieve significantly higher test results than the mechanical portable adhesion tester (Method B). When report ing results, ASTM D4541 requires report- ing the instrument used to conduct the test. The increase in test values using the pneumat ic or hydraul ic testers, compared with the mechanical adhesion tester, is significant, often doubling the value obtained using the mechanical adhesion tester. Other factors affecting test result values include the following: (1) the degree to which the surface is prepared prior to attaching the dolly, (2) the method by which the dolly is prepared prior to affixing it to the surface, (3) the adhesive selected, including the surface temperature during the cure of the adhesive and the time interval between attaching the adhesive and performing the pull. Prior to attaching the dolly, the coated surface is cleaned in a manner that does not affect the coating's integ- rity and does not leave a residue. The standard allows for light abrading of the coating using 400-grit sandpaper or finer, followed by solvent cleaning to remove particulates from the abrading process. The solvent selected must not compromise the coating's integrity. Data published by DeFelsko on its Website found that how a dolly is prepared can result in a significant 76 CoatingsPro J July 2012 difference in pull strength. The results indicate that preparing the dolly using Scotch-Brite pads resulted in an increased adhesion test value of 837 psi (5.77 MPa) compared to a machined dolly, and an increased adhesion value of 180 psi (1.24 MPa) compared to using sandpaper to abrade the dolly. Many di f ferent adhesives are used for adhering a dol ly to the coated surface. Generally, solventless, two-component epoxies provide the best results. Different types of epoxies are available, including some fast-set epoxies that reach their full strength and can be tested within 1 hour after application. The drawback for some fast-setting epoxies is a reduction in their maximum pull test strength. Slower curing epoxies generally require a 24-hour cure time, but they also allow for higher psi testing, some up to 5,000 psi. Selecting an epoxy that cures at the anticipated surface temperature is criti- cal. The time required between applying the adhesive onto the dolly and perform- ing the pull test is a function of surface temperature and epoxy formulation. For tests performed in accordance with ASTM D4541, at least three tests are required in the area tested to statistically characterize the area. General reporting requirements include the following: (1) general nature of the test (field or lab), (2) temperature and relative humidity during the test period, (3) details regarding the test apparatus used, and (4) a description of each coat in the coating system. Specific requirements related to the ABOVE Cohesion, adhesion, and glue failures illustrating proper location desig- nations in accordance with ASTM D4541. test results include the following: (1) the date, test location, testing location, (2) the values, nature, and locations of the failures (using the location designations included in ASTM D4541), and (3) if scoring around the dolly was performed. Certain coatings types, such as inorganic zinc (IOZ) primers, typically fail cohesively. For example, in a three- coat system consisting of IOZ primer, epoxy intermediate coat, and polyure- thane topcoat, the expected mode of failure is cohesive within the zinc primer. Therefore one should not be alarmed by a cohesion failure within the IOZ as long as the value at failure is at an acceptable level. Consult the coating manufacturer for its acceptance criteria. ASTM D6677 This adhesion test method uses a knife to determine the adhesion of a coating to a substrate or to another coating. Using a sharp knife, two cuts, each 1½" (38.1 mm) in length, at a 300 to 450 angle, are made in the coating film, forming an "X". The cuts must extend down to the substrate. The point of the knife is placed at the intersection of the cuts, and an attempt is made to lift the coating from the substrate or from other coating layers. Sufficient tests must be performed to ensure the adhesion evaluation is representative of the entire structure.