Performance Characteristics of
Zinc-Rich Coatings Applied to Carbon Steel
July 1973
By: William J.
Paton
Abstract
A program was conducted at Kennedy Space
Center to evaluate the performance of topcoated and untopcoated
zinc-rich coatings. Sacrificial coatings of this type are required for
protecting carbon steel structures from the aggressive seacoast
environment. A total of 59 commercially available zinc-rich coatings
and 47 topcoated materials were exposed for an 18-month period. Test
panels were placed in special racks placed approximately 30.5 m (100
feet) above the high tide line at the KSC Corrosion Test Site.
Laboratory tests to determine the
temperature resistance, abrasion resistance, and adhesion of the
untopcoated zinc-rich coatings were also performed.
It has been concluded that (1) The
inorganic types of zinc-rich coatings are far superior to the organic
types in the KSC environment, (2) Organic zinc-rich coatings applied
at 0.1 - 0.15 mm (4-6 mils) film thickness provide better corrosion
protection than when applied at the manufacturers' recommended
nominal film thickness of .08 mm (3 mils), (3) Topcoats are not
necessary, or even desirable, when used in conjunction with zinc-rich
coatings in the KSC environment, (4) Some types of inorganic zinc-rich
coatings require an extended outdoor weathering period in order to
obtain adequate mechanical properties, and (5) A properly formulated
inorganic zinc-rich coating is not affected by a 24-hour thermal
exposure to 400 degC (752 degF).
For additional information, a complete
copy of this study is available as a NASA Technical Note D-7336.
Send requests for copies to corrosion@ksc.nasa.gov .
To download a full copy of
this report in Adobe's pdf format for local printing, click d-7336.pdf.
(1.6MB)
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