Wash primer - etch primer?

I am getting grey hairs (more of them ) of these primers. I had everything ready, I was going to use Alodine and/or Zinc Chromate. Then it turns out that Zinc Chromate is illegal to use here because it is too toxic (according to some standards, but nevertheless), and therefore cannot be purchased anywhere, at least so I was told.

A local car/truck paint shop combined with aluminum/metal body (bus, truck, campers etc) maker had wash primer readily available. That is what they recommended to me, and I bought a litre (2 actually, a 1 to 1 mix) today, I'm going to test it later this evening. Just after I purchased the wash primer, I got the knowledge that although Zinc Chromate is illegal, it is optainable, and available for me to use. Ugh - go criminal or go wash? Allso, according to the tech sheet about the wash primer, it will stop- and protect against philliform corrosion - and - it will protect the metal even when damaged by stones that goes through the coatings and exposing the bare metal in a spot of limited size. How can it do that without some kind of nasty stuff helping it ? hmmm

But I started thinking, whash primer is that the same as etch primer? I thought so, but now I am in doubt. The wash primer I have is really thin, like water or even thinner. The etch primers I have seen in pictures etc looks more like a thick coating. Is this two completely different things?

The wash primer is industrial quality stuff, I have no doubt about that, It is made in France by Monopol and is called Wash Primer WG 6650. Does anyone here have any experience on this product? Anyone from France?

wash primer

Hi... the two terms, Self etching, or wash, mean the same thing. The idea is that mild phosphuric acid in the activator etches the metal on application. It is not a good idea to pre etch the metal if you are using either Wash or self etching primer. In the US, the product most use is DuPont Variprime.

HTH...Chris

I've used Variprime and Sherwin Williams P-60 wash primer and like the P-60 much better. It dries to a hard smooth finish that you can wipe dirt and oil off. The Variprime is soft and soaks up oil from your hands like a sponge. Anything strong enough to remove the oil removes the Variprime. Most of the primed areas on the inside of my RV-9A won't get any other coatings so I sure don't want a finish that shows every fingerprint and smudge. The Variprime is fine if you are going to Epoxy primer and paint over it in a timely fashion. That's just my opinion and we know what that's worth.

Variprime on aircraft

While IIRC, DuPont used to recommend Variprime for aircraft finishes, it's not in their current recommended aircraft paint systems...

http://www.performancecoatings.dupont.com/dpc/en/us/html/prodinfo/aviation/AVI_DAF_Recs_10-05.pdf

There are non-chromate epoxies available that should do the job, and DuPont even has an epoxy pre-treatment that replaces acid etch/alodine...

http://www.performancecoatings.dupont.com/dpc/en/us/html/prodinfo/aviation/AVI_DAF_Recs_10-05.pdf

gil A

Hi SvingenB,

I'm from Italy and I'm in the same situation as you (Alodine is not sold in Italy).

After long searches I found a few solutions:

1. AFS waterborne products, available in Europe through Aeropicardie in France. Unfortunatelly, Aeropicardie doesn't answered to my e-mails (after a first positive contact) and, even if I submitted an order, I didn't received any quote or any availability info. So, no AFS products for me (but you can try to contact them, maybe you are lucky!)

2. I contacted Sherwin Williams Italy and in a couple of days I was contacted from a technical rapresentative. He suggested me the following procedure:
- Wash aluminium pieces using DAL 238 (and/or Waterborne degreaser 4500080)
- Prime with Etch Primer 108.0990
- Prime with DTM Primer 108.0075

The etch primer doesn't add any thickness (so it can't be sanded), but only corrosion protection (good for interior surfaces). The DTM Primer is needed on surfaces that needs to be painted because ADD thickness and can be sanded before painting.

3. Another italian builder suggested me to use Lechler products. In detail:
- Wash aluminium pieces using 00695 Silicon remover
- Prime with 04318 Fix-O-Dur bicomponent wash primer.
I have still not enough information about this product but I think that an additional primer is necessary on exterior surfaces before painting (the Fix-O-Dur is compatible with nitro, poliuretanic and poliacrilic primers).

I have still not tested any of these products because I'm still not building because I'm waiting for the autorization from the ENAC (italian aviation agency) but I'll probabily use the Lechler products based on the experience of other italian builders.

Hope this help.

OK, thanks. Wash primer = etch primer, that's good. Tried the wash/etch primer yesterday, and it looks really good. It dryes in 5 minutes, and now after about 18-20 hours it is really hard and tough and I cant imagine it will ever fall off when the aluminium is scuffed with scotch brite (as it should according to the instructions). It looks like the stuff has become a part of the aluminium, a hard smooth thin cover.

I also contacted AFS in France, and for the price of the quote for the empennage only (400 €), I will get 27 liters of wash primer, probably enough for 5-10 airplanes!

All in all, I think I will go with the WG 6650 from Monopol for several reasons. It looks real tough, smooth and hard. It is thin and light, 10-15 micrometer, so it ads negligible weight (strange thing, according to the spec sheet, the thickness of the dry coating shall not exceed 45 micrometer). I had another talk with the truck body shop this morning where I purchased it. They use the stuff on trucks and trailers they make (steel and aluminium). When it is good enough for trucks being continuosly attacked by salt spray, pollution and small rocks, it sure must be good enough for the internals of an airplane. It has anticorrosive ingrediants, Zinc Oxide and Zinc Orthophosphate (I believe, but I'm not sure), it is supposed to protects the metal even when damaged to the bare metal. It is green (color that is) and legal

But most importantly, it is available here 10 min drive from my home and at a reasonable price, NOK 300 for 2 l (50 $ for 1/2 gallon). Insane opening hours though, 7 AM to 3 PM, so I have to cath them before work.

It is a bit of a mess to put it on, because it is two components that has to be mixed, then the cleanup when finished spraying.

Hex chrome

Yes, all of you in Europe, especially the Scandinavian countries, but soon all, have declared compounds and devices containing hexavalient(sp) chromium to be an SOC, or substance of concern, and is therefore to be banned. Unfortunately, alodoine is exactly that, and parts treated are included as banned; parts that are being recycled have to be noted and 'specially' desposed of. I'm in the middle of this with both my suppliers and my customers in Europe, and by proxy, GM, Ford and Damilier(sp, new name in the States, haven't learned to spell it yet), as even products intended for domestic use need to Hexchrome free by 2008.

Only problem is anything with similar properties is either hugely expensive or creates more toxic waste. Trivalent chromium based products may work for us, about 2/3 the corrosion resistance, but it won't work for boats and trucks. It also stinks.

Rick 90432 - alodining today, in fact, but treating the wastewater properly.

I got in contact with the producer. They say the correct way is to use wash primer (containing zinc oxide and phosphates) underneath a strontium chromate epoxy primer, then top coat(s). This will give optimum protection against corrosion, chemicals and mechanical abuse.

Is this as good as Alodine and zinc chromate? I have no idea, but it apperantly is good enough for airliners, which means it should be more than good enough for me (sounds logical although I am not sure exactly why ).