ASTM D7356-07

Acid etch damage is an important warranty claim item for automotive companies. As a result, acid etch resistance is an important parameter for automotive exterior coatings. The method described in this test method has been shown to simulate acid etch damage of automotive clearcoats that occurs when such coatings are exposed from May through mid-August in Jacksonville, FL.^{3 ,5} The accelerated test described in this standard allows year-round testing as opposed to the limited outdoor exposure time available for the Jacksonville, FL exposures.

1.1 This test method covers an accelerated exposure test intended to simulate defects in automotive clearcoats caused by acid rain that occur at the Jacksonville, Florida exposure site. Exterior exposures at an acid rain test location in Jacksonville, Florida produce etch defects that range from small pits to 12.7 mm (0.5 in.) in diameter or larger acid-etched spots. The latter type of defect is not produced in other acid-etch tests that only produce pits that are smaller than 6.35 mm (0.25 in.) in diameter.

Digital images of the acid etch defects produced in outdoor acid-rain exposures and in the accelerated test described in this test method are found in Appendix X1.

1.2 The accelerated test described in this test method uses a xenon-arc light source with daylight filter conforming to the requirements of Practice G 155. Specimens are sprayed with a simulated acid rain solution and requires the use of a horizontal, flat specimen array in order to allow the acid rain solution to remain on the test specimens for an extended period of time.

1.3 There is no known ISO equivalent to this test method.

1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.