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  #1  
Old 10-05-2015, 08:25 PM
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Vansconvert Vansconvert is offline
 
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Default Paint the exposed zinc chromate surface?

In the areas which are zinc chromated but do not readily show, such as between the wings and flaps, or, the trailing edge of the stabilizer, is the zinc chromate painted over with primer then color? Or just leave it in zinc chromate?
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  #2  
Old 10-06-2015, 09:02 AM
BillL BillL is online now
 
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Quote:
Originally Posted by Vansconvert View Post
In the areas which are zinc chromated but do not readily show, such as between the wings and flaps, or, the trailing edge of the stabilizer, is the zinc chromate painted over with primer then color? Or just leave it in zinc chromate?
When you are saying "zinc chromated" do you mean alodine? If so, personally, I use alodine on a lot of small parts and do not add a chromated primer on top. I have no specific data that says it is good. The reasoning is that the alodine will address the sandwiched alloy in the holes and edges, as the pure aluminum outer layer is pretty corrosion resistant on 2024 parts.

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Old 10-06-2015, 12:57 PM
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I have the same question. Do you use primer over zinc chromate before top coating?
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  #4  
Old 10-07-2015, 12:44 PM
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Come-on. There has to be a painting guru out there that knows the answer to this question.
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  #5  
Old 10-07-2015, 12:58 PM
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Are you referring to rattle can type Zinc Chromate primer?
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Old 10-07-2015, 01:08 PM
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PTI Zinc Chromate, aerosol, as sold by aircraftspruce
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  #7  
Old 10-07-2015, 01:19 PM
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I have never used any aerosol can Zinc Chromate paints that exhibited sufficient surface adhesion to be viable as a primer to use under a top coat. I have not used the particular product that you are referencing.

You may want to try a tape adhesion test to ensure the Zinc Chromate will not seperate from the base metal. I would also try priming and top coating some test samples of scrap metal to ensure the top coat is compatable with the primer.
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Old 10-07-2015, 01:24 PM
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Thanks for the recommendation
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  #9  
Old 10-07-2015, 07:13 PM
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Quote:
Originally Posted by Mike H View Post
I have never used any aerosol can Zinc Chromate paints that exhibited sufficient surface adhesion to be viable as a primer to use under a top coat. I have not used the particular product that you are referencing.

You may want to try a tape adhesion test to ensure the Zinc Chromate will not seperate from the base metal. I would also try priming and top coating some test samples of scrap metal to ensure the top coat is compatable with the primer.
+1 This rattle can is lacquer based. Many top coats need 2k primers. Definitely check.
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Old 12-27-2015, 07:43 AM
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To answer your question specifically. Alodine is what is none as a conversion coating or a metal prep. product. Another option to use as a metal prep that does not require any rinsing would be an acid etching wash primer. It is always advisable to use a metal prep under any primer whether that be a zinc chromate or an epoxy primer. When it comes to coating metals I prefer to use primers that contain chromates because chromates actively inhibit corrosion. As for topcoats to use over the zinc chromate primer, you need to use a single component topcoat. In other words if the primer does not require a catalyst then use a topcoat that doesn't require a catalyst. If you are trying to use a polyurethane topcoat to go over the primer then you should try the PTI Epoxy primer which contains Strontium Chromate. Strontium Chromate is part of the same Hexavalent Chromium family that Zinc Chromate is a Part of. Feel free to email me if you have more questions.
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