SYMPOSIA PAPER Published: 01 January 1996

Predicting Water Spot and Acid Etch Resistance of Clearcoats by Artificial Weathering: Acid Dew and Fog Test


The formation of water spots and acid etches at the surfaces of modern automotive basecoat/clearcoat systems occurs sporadically. This is caused by acid depositions and acid chemical attack during outdoor exposures. Currently used outdoor exposure tests in locations having a high incidence of acid rain, dew or fog, show often contradicting data of coating weatherability. This is because they depend on a large number of randomly occuring conditions like frequency, combination and acidity of the actual atmospheric precipitations. Current artificial weathering standardized test methods do not incorporate conditions such as controlled, introduced variables like acid depositions. The objective of our investigations was the development of an artificial weathering test for automotive finishes which includes the action of acid depositions, that will provide reproducibility and repeatability of test results. The conditions that result in environmental etch are examined and an improved artificial weathering test proposed.

Author Information

Schulz, U
BAM (Federal Institute for Materials Research and Testing), Berlin, Germany
Trubiroha, P
BAM, Berlin, Germany
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Developed by Committee: G03
Pages: 106–120
DOI: 10.1520/STP16155S
ISBN-EB: 978-0-8031-5342-4
ISBN-13: 978-0-8031-2407-3