Zinc based primer

Custom manufactured BBQ Pits, Do-it-Yourself projects, parts and ideas.

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Cas8101
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Zinc based primer

Postby Cas8101 » Thu Oct 11, 2018 8:47 am

Just completed a home shop built receiver hitch pit for the house and hauling to the deer lease for camp grilling. I've built a few pits and offset cookers and have always just ground the pipe down with a wire cup brush on my angle grinder then warmed the pit after cleaning the dust off and sprayed the pit with a few coats of rustoleun high heat paint. Served me pretty well, burns off here and there over the years and touch it up. Well I have seen some people suggest to have it blasted and then prime with inorganic zinc primer before painting. This is a new concept to me regarding pit painting. I always thought anything zinc related to be a big NO NO for cookers. Can someone enlighten me as to how this is a safe practice? Once it bonds to the metal it can't off gas on the external paint job? I have access to inorganic zinc primer but it's only rated to 750 degrees. I'm not sure my pit would ever get that hot but I wouldn't doubt it when I light a big fire in there to burn down to coals that I could be near that threshold for an hour or so while it burns down.
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k.a.m.
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Re: Zinc based primer

Postby k.a.m. » Thu Oct 11, 2018 11:07 am

I have all my cookers blasted and primed with inorganic zinc. You do not paint the inside it is an outside coating that lasts. The hottest I have ever gotten the top of my firebox was about 675° well below the primers rating.
Always remember slow and steady wins the race.



My Hybrid cooker.
Competition trailer #2.
Cas8101
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Re: Zinc based primer

Postby Cas8101 » Thu Oct 11, 2018 1:05 pm

Well I may just give it a go then. What about repainting when the time comes? That primer will be bonded to the metal so do you just scuff up the high heat top coat and re paint and not worry about repriming?
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Re: Zinc based primer

Postby k.a.m. » Thu Oct 11, 2018 10:15 pm

I have never had to re-coat one of my cookers the top coat has been on for about two years on my little trailer mount and 7 years on my big cooker.
Always remember slow and steady wins the race.



My Hybrid cooker.
Competition trailer #2.
Cas8101
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Re: Zinc based primer

Postby Cas8101 » Mon Oct 29, 2018 6:21 pm

Got around to painting my pit today, question for y'all I applied two oats of rustoleum BBQ black to a preheated pit via a propane cactus burner. Painted outside in the shade and thought all was well and cleaned up my gun and cracked a beer. Couple hours later I inspected it and can see i didn't get even coverage or paint dried instantly in some spots because maybe the pit was heated to much. Not a uniform appearance. Flatter looking areas mixed in with the mostly satin finish on the majority of the pit. If I give it one more coat tmrw to try to even out the finish do I need to preheat again and do I need to rough the previous applied paint up?
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Re: Zinc based primer

Postby dwilliams35 » Tue Oct 30, 2018 7:56 pm

Cas8101 wrote:Got around to painting my pit today, question for y'all I applied two oats of rustoleum BBQ black to a preheated pit via a propane cactus burner. Painted outside in the shade and thought all was well and cleaned up my gun and cracked a beer. Couple hours later I inspected it and can see i didn't get even coverage or paint dried instantly in some spots because maybe the pit was heated to much. Not a uniform appearance. Flatter looking areas mixed in with the mostly satin finish on the majority of the pit. If I give it one more coat tmrw to try to even out the finish do I need to preheat again and do I need to rough the previous applied paint up?

Why the preheat? If you look at the technical sheet for rustoleum bbq paint:
https://www.rustoleum.com/~/media/Digit ... t_TDS.ashx
It says apply between 50 and 90 degrees F., then after it’s dried you cure it at 450... sounds to me like it would just dry too quickly and not get the bond it’s really capable of,..
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Re: Zinc based primer

Postby Cas8101 » Tue Oct 30, 2018 8:28 pm

The main reason I preheat is because where I live it's high humidity. You can see the moisture evaporating before your eyes when you heat the steel with the propane burner. That moisture if left would surely hinder the paints adhesion IMO. Only heat the pipe to maybe 125-150
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Re: Zinc based primer

Postby Cas8101 » Tue Oct 30, 2018 8:31 pm

I scuffed the pit today with some 220 grit then blew it off and wiped it down with a dampened rag with mineral spirits to remove the dust, then hit the pit with one more light coat. It evened everything out and I am pleased.
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Re: Zinc based primer

Postby dwilliams35 » Tue Oct 30, 2018 8:34 pm

Cas8101 wrote:The main reason I preheat is because where I live it's high humidity. You can see the moisture evaporating before your eyes when you heat the steel with the propane burner. That moisture if left would surely hinder the paints adhesion IMO. Only heat the pipe to maybe 125-150

I don’t think you’re any higher humidity than myself, or k.a.m for sure: I’d say if you have a concern, wait for a good dryish day, go ahead and heat it up to dry it out, then let it cool down to ambient temp before painting. Paint needs time to cure, rushing it like that doesn’t generally do it any favors: that’s why they limit it to 90 in the instructions..
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Re: Zinc based primer

Postby Cas8101 » Tue Oct 30, 2018 10:14 pm

dwilliams35 wrote:
Cas8101 wrote:The main reason I preheat is because where I live it's high humidity. You can see the moisture evaporating before your eyes when you heat the steel with the propane burner. That moisture if left would surely hinder the paints adhesion IMO. Only heat the pipe to maybe 125-150

I don’t think you’re any higher humidity than myself, or k.a.m for sure: I’d say if you have a concern, wait for a good dryish day, go ahead and heat it up to dry it out, then let it cool down to ambient temp before painting. Paint needs time to cure, rushing it like that doesn’t generally do it any favors: that’s why they limit it to 90 in the instructions..

Thanks for the advice, if this paint job fails quick than I will certainly give your method a try next time. I suspect my pit was around 90 degrees by the time I started painting though. I heat it up, then get my gun setup then paint the pit while its warm to the touch of the hand.
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k.a.m.
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Re: Zinc based primer

Postby k.a.m. » Wed Oct 31, 2018 6:02 am

The heating of the steel created a flash point for the paint in other words it dried too quickly. Painting in high humidity is not your enemy a high dew point is. Apply a light "Wet coat" over what you have but not too heavy or it will orange peel on you.
Always remember slow and steady wins the race.



My Hybrid cooker.
Competition trailer #2.
Cas8101
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Re: Zinc based primer

Postby Cas8101 » Fri Nov 09, 2018 2:40 am

k.a.m. wrote:The heating of the steel created a flash point for the paint in other words it dried too quickly. Painting in high humidity is not your enemy a high dew point is. Apply a light "Wet coat" over what you have but not too heavy or it will orange peel on you.

Scuffed it the next day then applied a thin coat over everything. Came out great, even color. I let dry for 24 hours then ran a small fire in it around 250 for a couple hours then cranked her up to 400 for a couple hours to heat cure the paint, seasoned the inside at the same time. Have cooked on it four times, no orange peeling and stuck really well to the sandblasted metal. Came out real nice.

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