Zenith Aircraft Builders and Flyers
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Zinc Chromate (Cortec) Primer source
Hi guys
Was trying to source the zinc chromate primer that is brushed on. . I ve done a search on here and online but not found a link to a source. is it not sold anymore?
Ive also seen the brand name cortec talked about, is that a good substitute for the old Zinc Chromate?
If so whats a good source for cortec, I could not find it on aircraft Spruce.
Thanks guys
Michael in Toronto
Replies to This Discussion
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Permalink Reply by John Austin on
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I don't know if Zinc Chromate is still sold or not, but it is highly toxic. Cortec is recommended and used by Zenith. Normally, it is only available in large commercial quantities, but Zenith repackages and sells it in smaller affordable quantities for homebuilders. You can dilute it with water to get a consistency you can spread with a brush (I used cheap foam brushes and just threw used ones away each time after use) - a thin layer is all you need. It dries fairly quickly, but the former engineer at Zenith said it is perfectly OK to assemble parts while the Cortec is still wet - however, if you do assemble it wet, it acts like a glue when dry and makes it difficult to disassemble parts, so only do this in a final assembly that won't be taken down again!
John
N750A
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Permalink Reply by Loren Warner on
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We used Cortec and Zinc Phosphate spray for our build. The Cortec between all adjoining surfaces, and sprayed the Zinc Phosphate in all areas that will not normally be readily accesible. As John said, let the cortec dry before final assembly. Besides, if you spread on thin as you should, it only takes 5 minutes to dry.
Being in cold country, the Cortec is wonderful to work with because we don't need ventilation protection, or worry about overspray.
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Permalink Reply by Lawrence Bird on
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Check Amazon and/or marine outlets for zinc-chromate... getting pricier, but generally available...
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In my opinion you should avoid chromates due to it being a known carcinogen. Zinc phosphate paints are carried by our local aircraft supply stores and likely available near you are well.
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Permalink Reply by John A. Minatelli on
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Hi Michael,
Cortez is natural latex stabilized with ammonia and it works great for all contact surfaces however an etching primer for aluminum form rustoleum followed by any spray paint will protect all none contact surfaces. This avoids the use of chromates entirely which are indeed quite toxic.
John Minatelli
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Permalink Reply by Ghazan Haider on
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HI Michael, I get my Zinc Chromate from the Aircraft Spruce in Brantford. They had the brush-on version in a bigger can last time I was there, but I've only purchased the spray and use wipes to 'brush' it. The reason being that my build goes so slow that previous half-filled cans have jammed and any open container might get too dried up (but that's me).
When I first went there about 7 years ago they said there's a chemical company down the street in Brantford which manufactures zinc chromate and they can sell larger quantities cheaper, I'd have to drive there. I just purchased the cans back then. So I think it is either the people at the store who would know (or Mark Townsend) about the location of that chemical company if you're still looking for a local source.
Many others here have supported the Canadian Tire version as well. To me it was too thin and I was quite ok with paying $2 more for an 'aircraft version' but the base chemical composition should be the same.
Hope this helps.
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Permalink Reply by Michael T. on
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Is this the Zinc Chromate primer I should use, that Zenith is painting on?
https://www.aircraftspruce.com/catalog/cspages/ptiprimers.php?click...
I was wondering, is the epoxy primer as good?alumiprep, alodinme then epoxy?
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Permalink Reply by Joe Spencer on
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the epoxy primer(Randolph, Polyfiber) is hands down better than ZC but not as easy to handle...it's 2 part and has a pot life but if you put it in the freezer between sessions it will still be usable a year or more later. I got some in the freezer that's been there several years and it's still fine for spraying or brushing. Another excellent primer is Dupont Variprime also a 2 part(that's what I used) It sticks and is tough. ZC can be wiped off with a MEK rag and doesn't stick near as well as either of the 2 parts but it's easier to use; that's the only advantage I know of. I've applied ZC with the same surface prep as the 2 parts and washed it off with a pressure washer. I never use the popular prep systems; just wipe it down with rubbing alcohol and clean paper towels, then scuff it good with 3M purple scuff pads then wipe it down with alcohol again and shoot it. One WET coat of primer is all that's necessary. That's always worked for me except with ZC; did that on 6 planes and many misc jobs.
But in lap joints yeah it's fine if that's what you wanta use.
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Chief Aircraft only sells zinc phosphate. Identical to zinc chromate. I used BondeRite as an etch, Aldoine then sprayed zinc phosphate. I also applied Cortec by brush on other parts. Really good stuff.
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Permalink Reply by Joe Hopwood on
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Zinc chromate, ZnCrO4, is a chemical compound containing the chromateanion, appearing as odorless yellow powder or yellow-green crystals, but when it is used for coatings pigments are often added.
Zinc phosphate (Zn3 (P O4) 2) is an inorganic chemical compound used as a corrosion resistant coating on metal surfaces either as part of an electroplating process or applied as a primer pigment.
Hardly identical.
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the zinc phosphate I've used is junk. it takes forever to get hard(never really does) and easily wiped off with thinner. lotsa better stuff out there in my experience
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