Factors Influencing Cathodic E-Coat Primer Cratering on Zinc-Rich Surfaces

850237

02/01/1985

Event
SAE International Congress and Exposition
Authors Abstract
Content
Cathodic electrocoat primers (e-coat) have been adopted by automobile manufacturers worldwide due to their advantages with regard to application and corrosion resistance. Tests in the laboratory and production experiences have shown that, when deposited at sufficiently high voltage, e-coat primers form rough, cratered films on zinc-rich coatings. In addition to causing a visibly unacceptable surface texture, cratering adversely affects the corrosion protection afforded by the e-coat by providing paths for corrodents to reach the metal substrate. The occurrence of cratering at various production and laboratory electropaint facilities has been inconsistent. In order to explain some of these inconsistencies and identify means to reduce cratering, we studied the influence of various e-coat deposition process variables on the incidence of cratering. Our findings show that cratering resistance is increased by: (1) minimizing AC ripple of the rectifier, (2) decreasing the rate of voltage application during deposition, and (3) increasing anode to sample separation.
Meta TagsDetails
DOI
https://doi.org/10.4271/850237
Pages
8
Citation
Hart, R., "Factors Influencing Cathodic E-Coat Primer Cratering on Zinc-Rich Surfaces," SAE Technical Paper 850237, 1985, https://doi.org/10.4271/850237.
Additional Details
Publisher
Published
Feb 1, 1985
Product Code
850237
Content Type
Technical Paper
Language
English