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I have both aluminium and mild steel items to go on the MiniMax I'm building.

 

What paint should I use as an anti-corrosion primer, and where can I get it (online/mail order)?

 

Many thanks in advance

 

Bruce

 

 

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Bruce,

 

I am about to start painting my Sierra & as anyone will tell you preparation is the most important part.

 

The best aluminium preparation product, used on all US military aircraft & by most manufacturers is Prekote from Pantheon Chemicals. It replaces alodine or any chromate product & is non toxic unlike those other products. It can be used on all metal & composite surfaces. It is applied with fine scotchbrite pads & lathered up. This is done twice without rinsing & then a full water rinse. I got a 1 US Gallon container from Aviall via a LAME as they won't sell to Joe Public but it can be purchased from other Aviation retailers. Not cheap but no really good products are.

 

Within 24 hours you then use a good quality epoxy etch primer. I am using Hi-Chem Super Etch. Another is Wattyl Super Etch. Just make sure it is an Epoxy. Once this is applied you can wait months before putting on base coats & finish coats. The primer seems to take about a week to fully etch the metal as even after it is dry & hard you can still scrape it off with your finger nails but once it has aged it is there forever. Check out www.pantheonchemical.com

 

Kevin

 

 

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Within 24 hours you then use a good quality epoxy etch primer. I am using Hi-Chem Super Etch. Another is Wattyl Super Etch. Just make sure it is an Epoxy. Once this is applied you can wait months before putting on base coats & finish coats. The primer seems to take about a week to fully etch the metal as even after it is dry & hard you can still scrape it off with your finger nails but once it has aged it is there forever. Check out

Why use a surface preparation and then use a etch primer? the organic acids [in the etch primer] will remove any such surface prep including alodine. Just use a two pack epoxy primer .If you want to use an etch primer just clean [aluprep] the surface to be painted.Cheers
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I used Protec Proetch, bloody disgrace, what ever you do it ends up all furry and you spend hours sanding it back off to get it smooth, I ran out of it and got some Altak Altra-etch, entirely different experience, goes on smooth, just a gentle rub with scourer and it is ready for top coat.

 

 

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Why use a surface preparation and then use a etch primer? the organic acids [in the etch primer] will remove any such surface prep including alodine. Just use a two pack epoxy primer .If you want to use an etch primer just clean [aluprep] the surface to be painted.Cheers

Etch primers are not the panacea for surface preparation. If they were then aircraft manufacturers & the military would not use Prekote. Rec aircraft are not subjected to the same environments as commercial & military aircraft but by using such a product you get much better bonding. If you live in a harsh seaside type environment longevity will be much enhanced. Aluprep is a soak acid product which prepares the surface for chromating or etch priming. It is pretty corrosive so timing is critical before the wash rinse.

 

"PreKote cleans the surface to be painted while enhancing the adhesion of coatings and improves corrosion protection - all with a superior, non-hazardous and safe technology. This easy-to-apply process deposits a molecular layer that bonds to the surface of metal or composite material. This layer allows the coating, when applied, to get closer to the substrate surface than traditional pre-treatments creating a stronger bond with the surface.

 

PreKote also provides a polar/non-polar molecule that attaches itself to permanently imbedded contamination; this molecule attracts the coating. In contrast, traditional conversion coatings containing heavy metals such as chrome or zinc have no mechanism by which to attach themselves to permanently imbedded contamination. Since the coating cannot attach itself to those areas, it is a common cause of coating blisters, outgassing (pinholes), skips, etc."

 

 

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Since the MiniMax has a small amount of aluminium and steel, I wouldn't go all out on prep and prime work.

 

Clean it up good and shoot some etch primer on it, then a top coat lacquer or something to seal.

 

As an example of what some might call overkill, the majority of my Sonex is 6061-T6 aluminium. All interior and mating surfaces were prepped with Prekote, then spray painted with Wattyl Super Etch in one or two fine coats (weight).

 

The biggest downside was the amount of time it took to scrub, rinse, dry, paint, dry, assemble! Manufacturers will tell you 6061 does not corrode... but it does.. just let some fine dust accumulate on it in the shed and let cold moist air settle on it.. how fast can you say filliform?

 

Although Wattyl super etch is supposed to be an epoxy it is quite soft and can be removed with methylated spirits or even thread cutting oil. In the cockpit area I clear coated it.

 

If I were to build again I probably would only prime mating surfaces.

 

For me alodine and alumiprep were too hazardous to use.

 

Regards

 

Tony

 

 

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Etch primers are not the panacea for surface preparation. If they were then aircraft manufacturers & the military would not use Prekote. Rec aircraft are not subjected to the same environments as commercial & military aircraft but by using such a product you get much better bonding. If you live in a harsh seaside type environment longevity will be much enhanced. Aluprep is a soak acid product which prepares the surface for chromating or etch priming. It is pretty corrosive so timing is critical before the wash rinse."PreKote cleans the surface to be painted while enhancing the adhesion of coatings and improves corrosion protection - all with a superior, non-hazardous and safe technology. This easy-to-apply process deposits a molecular layer that bonds to the surface of metal or composite material. This layer allows the coating, when applied, to get closer to the substrate surface than traditional pre-treatments creating a stronger bond with the surface.

 

PreKote also provides a polar/non-polar molecule that attaches itself to permanently imbedded contamination; this molecule attracts the coating. In contrast, traditional conversion coatings containing heavy metals such as chrome or zinc have no mechanism by which to attach themselves to permanently imbedded contamination. Since the coating cannot attach itself to those areas, it is a common cause of coating blisters, outgassing (pinholes), skips, etc."

Aluprep is mainly used to remove the oxide layer on Al prior to alodine application which is a chemical form of electro-plating to aid corrosion resistance and paint adhesion .Using an etch primer will remove the alodine and also any other surface/substrate preparations . Being using aluprep-alodine -paint [single coat zinc chromate or zinc oxide] then a top coat method for over 40yrs and find them to have lasted the longest to date. I have used Prekote for the past 6yrs and only so time will tell how it will go under the two pack epoxy primer [NOT etch primer] followed by two pack acrylic top coats.Where the heck are you getting your info to use an etch primer??? as you are just quoting straight from the prekote pamphlet. cheers
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Thanks to all. As ever, lots of differing opinions!

 

Since I only have small amounts of metal to 'paint', if I go the etch prime only route, where can I get some? (I'm in country NSW so has to be posted).

 

Thanks

 

Bruce

 

 

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