Summary for corcoat 5803 Discussion
Corcoat 5803 is discussed as a possible alternative to Alodine 1200/1500 for aluminum conversion coating, especially for a communications company using it as both a pre-paint treatment and a stand-alone finish. The original poster asks for detailed performance data such as wear and electrical insulation, and also whether a coating that meets European directives but lacks U.S. military approval can still be acceptable. Ken Vlach advises contacting Coral Chemical for Corcoat 5803 information, noting that the hexavalent-chromium Corcoat on QPL-81706 is manufactured for Coral by MacDermid. He also suggests considering MacDermid’s non-hex Iridite NCP and points to ASTM B921-02 as an applicable standard for non-hexavalent chromium conversion coatings on aluminum; he adds that he is unaware of a specific ISO non-hex chromium standard, but ISO 10546 may be used as a performance reference. Alexander Westbrook later says he does not know Corcoat 5803 specifically, but suggests that moving from Type I to Type II conversion coatings may be the easiest path for Class III applications.
Q. I have been tasked with finding an alternative for Alodine 1200 and 1500 (thank you Europe). We are a communications company and we coat ALL our products with Alodine as either a pre-paint process or as a stand alone finish. My search has lead me to Corcoat 5803 as an alternative but I cannot find any additional information on the coating. I understand it meets MIL spec but has not been approved and so my question is 2 fold:
1. Obviously, does anyone have detail specifications on the plating performance (wear, is it electrically insulating or not, etc.)
2. If the plating conforms with the European Directive but has not been MIl spec approved, under what guidelines is this acceptable? even though it has not been approved by our (U.S) military specification.
Gerardo G. Huerta
Clearcom Communications – Emeryville, California, U.S.A
2005
Contact Coral Chemical for Corcoat 5803 information. coral.com/
As the hex.-Cr Corcoat on QPL-81706 is manufactured for Coral by Macdermid, perhaps you should also consider MacDermid’s non-hex. Iridite NCP: macdermid.com/industrial/aluminum.html
An applicable standard is ASTM B921-02 “Standard Specification for Non-hexavalent Chromium Conversion Coatings on Aluminum and Aluminum Alloys.”
I am unaware of an ISO non-hexavalent chromium standard per se. Perhaps require performance to ISO 10546 (1993) “CHEMICAL CONVERSION COATINGS – RINSED AND NON-RINSED CHROMATE CONVERSION COATINGS ON ALUMINIUM AND ALUMINIUM ALLOYS.”
Ken Vlach [deceased]
– Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
A. I do not know about Corcoat 5803, but if you need to move from Type I conversion coatings there are a decent amount of Type II conversion coatings that work well for Class III applications. I would think using those is the path of least resistance.
V/R
Alexander Westbrook
– Waldorf, MD
October 30, 2025