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CUI vs Zinc Primer 1

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Doodler3D

Doodler3D

Mechanical
Jan 20, 2020
188
Hi,

In a supply chain mix-up, the supplier delivered a high temp CUI primer instead of a silica-zinc primer. The lead times to get the correct coating is eight weeks while the equipment is scheduled to ship out in a week. Both primers are rated for 1000F while actual application will see a maximum of 120F on the coast in tropical environment. The device is a part of a fuel feed system that does not need insulation. Would both coatings provide similar resistance to corrosion?

Thank you.
 
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The zinc rich primer protects the metal in the event of defects and damage of the coating. I would not suggest this substitution for your application.

Does the CUI primer have good UV resistance?

Most coatings manufacturers have parallel lines of products. If your supplier can't provide the coating within your time requirements you may find a supplier with a similar coating that can.

On top of zinc-rich primer, include terms such as epoxy, surface tolerant and high build to help narrow down a suitable alternative.

Topcoating can provide UV resistance if your anti-corrosion coating can't provide it.
 
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I can't open the data sheets for some reason. Can you tell us the mil thickness of each coating. The Zinc primer looks like it's meant to go under the 1000 primer. Anti-corrosion coatings typically require a minimum thickness of around 20 mil and the zinc rich primers in my experience only give 2-5 mil so they require additional coats of anti-corrosion primer on top.
 
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TugboatEng,

Primer base: Temperkote 1000 primer, DFT 125 μm (5.0-6.0 MILS/COAT), Total coats = 1
Link

Top Coat: Temperkote850 Alkyd Silicone resin, DFT 30 μm (1.2 MILS/COAT), Total coats = 2
Link

The primer should have been Temperkote zinc primer
Link
 
 https://files.engineering.com/getfile.aspx?folder=7580aa11-f332-41cc-9d05-f851c29da3a9&file=TemperKote1000.pdf
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I still can't view the zinc primer spec but can view the 1000.

My understanding is that these products are not substitutes for each other. You can use the 1000 without the zinc but will not get as good of protection. You cannot use the zinc without the 1000, if my understanding is correct.
 
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Did anyone spot the warning on the 850 datasheet: "DO NOT USE OVER GALVANISED METAL OR ZINC RICH COATINGS." Perhaps that's why the Zinc Primer datasheet doesn't offer 850 as a suitable topcoat.

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.
 
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Dr Jones, there was a mix-up and the wrong coating was advised/supplied.
 
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So, you needed TemperKote 850 Primer? The 850 was NEVER going to go over TemperKote Zinc Primer.

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.
 
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They appear to have both a topcoat only and a primer in the 850. OP's link shows the topcoat.
 
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@Tug,

Indeed, and I’m pointing out that for the 850 topcoat, the OP needed the 850 Primer

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.
 
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I'm a little confused. OP should be using the Zinc under a coat of Temperkote 600 or 1000. The 850 would be optional but could be applied to the 600 or 1000. OP will lose a lot of corrosion performance if the zinc coat is skipped.
 
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Gentlemen, Thank you. The end user agreed to what was available at the earliest, i.e., a 1000 primer with the 1000 topcoat.

Do books like ASM Handbook, Volume 5B: Protective Organic Coatings do a good job of listing compatibility between different coating formulations? For example, if incompatible coatings may saponify or undergo cathodic debonding?
 
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For topcoating of zinc rich primers: SSPC-PS Guide 8.00 along with manufacturer's datasheets.

A reasonable first start for coating selection can be made from most of the major players' web sites such as Hempel

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.
 
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Dr Jones, thank you for the recommendation. In a coating system, does the alkyd chain of a modified silicone alkyd resin react with zinc?
 
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@Doodler

Given the warning on the 850 datasheet, one would have to say yes, for that specific 850 formulation.

Why on earth are these coating systems being selected for an aggressive CX environment at a notional 48 deg C (not allowing for temperatures generated by solar radiation)?

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.
 
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Dr Jones, it's a one-size-fits-all approach for coatings. Unfortunately, I'm not the one in charge.
 
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