ASTM D2794-93 (R2019) pdf free download.Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact).
1.1 This test method covers a procedure for rapidly deforming by impact a coating film and its substrate and for evaluating the effect of such deformation.
1.2 This test method should be restricted to testing in only one laboratory when numerical values are used because of the poor reproducibility of the method. Interlaboratory agreement is improved when ranking is used in place of numerical values.
1.3 The values stated in inch-pound units arc to be regarded as standard. The values given in parentheses arc mathematical conversions to Si units that arc provided for information only and are not considered standard.
4. Summary of Test Method
4.1 The organic coatings under lest are applied to suitable thin metal panels. After the coatings have cured, a standard weight is dropped a distance so as to strike an indenter that deforms the coating and the substrate. The indentation can he either an intrusion or an extrusion. By gradually increasing the distance the weight drops. the point at which failure usually occurs can be determined. Films generally fail by cracking. which is made more visible by the use of a magnifier, by the application of a copper sulfate (CuSO4) solution on steel, or by the use of a pin hole detector.
5. Significance and Use
5.1 Coatings attached to substrates are subjected to damaging impacts during the manufacture of articles and their use in service. In its use over many years. this test method for impact resistance has been found to be useful in predicting the performance of organic coatings for their ability to resist cracking caused by impacts.
6. Apparatus
6.1 Testei; consisting of a vertical tube to guide a cylindrical weight thai is dropped on a punch resting on the test panel.
6.1.1 Guide Tube, 24 w 48 in. (0.6 to 1.2 m) long mounted vertically in a base plate. A slot is cut lengthwise on one side of the tube to act as a guide for a cylindrical weight that fits inside the tube. Graduations are marked in inch-pounds along the slot. The base is constructed so that a thin flat panel can be inserted at 2 in. (50 mm) below the tube.
6.1.2 Weight, metal cylinder, made to fit inside the guide tube. A pin is fitted into one side of the weight to act as a guide by riding in the slot of the tube and to serve as a handle by which the weight can be raised and released and serve as the indicator of inch-pounds (kilogram-metres).ASTM D2794 pdf download.