I need some advise in regards of painting my Seabee which I am presently restoring. The whole airframe is soda blasted and all corrosion is removed. With all the new products out there do I still have to acid etch first, then use a conversion coating followed by epoxy primer and polyurethane paint? Or is there a simpler way to achieve good results? A friend has a car paint booth available, however I can't acid etch or conversion coat at his place as it is quiet messy.

Call Stewarts They have the product that will work I believe without all the Hassles!
http://www.stewartsystems.aero/

During my time at Kenmore Air Harbor I was involved in painting perhaps 30 seaplanes. We used acid etch, alodine, epoxy prime and polyurethane exclusively. Usually these projects also involved extensive sheet metal repairs where we would repeat this process for every skin that went on. All skin seams were sealed with 2 part semkit as well.

Keep in mind these planes were all destined to operate in the salt water environments of the Pacific NW and Alaska so corrosion control was of utmost importance. Even with all this we still found it necessary to repaint the airplanes every 10-12 years

If your airplane is never going in the salt you can get away with less methinks. My friends at Wipaire had freshwater airplanes they would work on that had very little corrosion problems. That's maybe why they thought they should build floats out of 6061 aluminum but that's another discussion entirely

So my advice is if you ever plan a trip to the coast you best go thru the motions of full prep.

Absolutely what Halestorm said. A thourgh scrubing using acid etch and scrub pads followed by Alodine conversion process. There is NO substitute! Don't let anyone try to talk you into using a "Greenie " proceess! I strongly suggest Jet Glow. You get what you pay for. It flows out real nicely and wears like iron. Very user friendly for a part time painter. You MUST be fully protected with a paint suit and fresh air breathing system when using any paint with a Isocyanite hardner. Try to cut corners and you're going to have paint coming off in sheets from the bottom of your hull. Do right the first time and do it once.

I third the notion of acid etch and alodine for a SeaBee. I wouldn't even THINK of doing anything else.

Consider all the effort and expense you're going to in this restoration, and consider the consequences of a failed coating.......ugly.

Acid etch and alodine isn't fun, and it is messy, but it is still the standard for seaplanes, in my opinion, and that of most in the seaplane world.

MTV

There's a Commercial operation around my area, that after alodining, uses a primer product called Super Koropon, on all their saltwater fleet. Weird name, but it was developed by Boeing for use in aerospace applications. The Stewart system is a water based urethane, from what I have seen, it can be a little finicky, and has had some anomalies with regard to high moisture environments. I would stay away from this "green stuff" for this application, as mentioned above. Closed areas with high humidity and corrosive liquids call for the nasty, hydrocarbon- isocyanate stuff. It's been proven to work.

Stewarts is waterborne, not waterbased. That being said, it's great stuff, If you can follow directions...I'm gonna go out on a limb here (but not far) and say all the "nay sayers" haven't used it. I have... for about 15 years. It's more flexible than anything out there, and as tough as any.
With any paint job, the prep is 90% of the job. Take a short cut there, and you'll pay for it somewhere down the road. Halestorm has given you some good advice, you wont be sorry to follow it.
John

Just be sure to read the MSDS for the paints before using Stewarts. This stuff is far from non-toxic, with high levels of isocyanates.

Just be sure to read the MSDS for the paints before using Stewarts. This stuff is far from non-toxic, with high levels of isocyanates.

Yes, you certainly don't want to drink it!

While still rich in isocyanates, Stewarts paint (and other waterborne polyurethanes) keep the dangerous stuff much more effectively encapsulated whilst in an active state than the traditional high VOC solvent based paints. This protects our delicate mucus membranes and keeps us happy. As someone who's had isocyanate poisoning (twice dammit!) I'm all in favor of keeping my personal mucus membranes happy.

Stewarts paint is awesome, it's pretty much all I'm using anymore. It is however much lower in solids than other paints and maybe not the best choice for a seaplane. Maybe a bunch of coats?

Same here Halestorm (isocyanate poising). Stewarts may not be as high in solids as some of the solvent borne paints, but it's just as durable. I'd have no problem recommending it for seaplanes.
A little "primer" on how isocyanates work might be in order here....
Yes, they are a form of cyanide...that's what makes a polyurethane "work". So any polyurethane will have a level of isocyanates in it. The isocyanates are attracted to moisture/water, and being made up of primarily water, our bodies are a wonderful receptor for them..in fact we attract them, primarily through our soft tissues (eyes, nose, ears, mouth, etc.). They behave just like electricity in that they "follow the path of least resistance", therefore when added to a waterborne mixture, they're pretty much happy to stay there, thus making the waterborn polyurethane much safer to apply. However, the most dangerous time for ANY isocyanate catalyst is when you're mixing, as the catalyst is "free" and seeking a "happy place" to be. Therefore, protection is warranted when mixing....and I don't know how many times I've seen people mixing with no mask, gloves, suit, etc....and yes, I did it too, back when I thought I was bulletproof. I now have the scars and problems to prove it.
Working with a water borne paint isn't that difficult...but it sure is different from a solvent borne paint, and that's where a lot of the "problems" pop up. I used to teach classes on it, and the worst ones were guys that had shot solvent borne for years. Old habits are hard to break... I know, I have to keep reminding myself too! I always compare it to flying a taildragger.... if you land your taildragger with the same technique that you do a 172, you're most likely not going to receive the results you're looking for. Neither are impossible, nor even that terribly difficult, but they are two different sets of techniques.
John

Thank you for all the replies and info. The Super Koropon primer sounds great. It looks like I will acid etch, alodine, then Super Koropon primer with a polyurethane top coat.

Ok now wait another minute. I believe primers like Super Koropon and BMS 10-11 are designed to be stand alone and not necessarily top coated, too hard and shiny for good adhesion. Most real polyurethanes require a compatible primer to stick the best, usually part of the same family. Whatever you use, Imron, alumi-grip, Centari or whatever. If you do top coat Super Koropon it's going to need a good scuffing with red scotch brite or something first. Also would be best to shoot top coat as soon as possible over "green" primer, as in young and fresh.

Halestorm wrote:Ok now wait another minute. I believe primers like Super Koropon and BMS 10-11 are designed to be stand alone and not necessarily top coated, too hard and shiny for good adhesion. Most real polyurethanes require a compatible primer to stick the best, usually part of the same family. Whatever you use, Imron, alumi-grip, Centari or whatever. If you do top coat Super Koropon it's going to need a good scuffing with red scotch brite or something first. Also would be best to shoot top coat as soon as possible over "green" primer, as in young and fresh.

PPG PRC-DeSoto Super Koropon fluid resistant interior primers are conventional solids, chemically cured, lead and cadmium free epoxy primers. These high performance primers are formulated to protect the interior of aircraft corrosion. PPG PRC-DeSoto Super Koropon fluid resistant interior primers have excellent adhesion to a variety of sub- strates and exhibit a high degree of Skydrol resist ance. These primers have been used successfully on a wide variety of aircraft throughout the world.
PPG PRC-DeSoto Super Koropon fluid resistant interior primers are compatible with all non-electrostatic application equipment and are easy to spray. For further details on the application parameters for these primers, consult the application guide for Super Koropon fluid resistant interior primers or contact your local PPG Aerospace Application Support Center.

If you do go with the Stewart System or not, here is a good forum for there product.
Good Luck and have fun
http://www.stewartsystems.aero/forums/default.aspx

To start with I should mention that most commercial operators swear by lacquer with alluminum powder mixed into it. It is fairly corrosion resistant and easy to repair. I don't necessarily think that is the way to go for your Seabee. I would not use interior primer anywhere except the interior. Your best bet is probably the etch, conversion coat, epoxy prime, topcoat with urethane or polyurethane. It sounds like the soda blast has gotten you down to good clean metal including removal of the original conversion coating(Alodine). No reason to get to crazy with the etch. The acid is meant to react with the oxidized metal to remove it. Since that is already removed, you just need a very mild solution to neutralize any residual soda and remove oil and dirt so the alodine will stick. It is possible that the alodine will stick without the etch, but I would not chance it. Etching and alodining is far less toxic than painting in my opinion. The etch you formulate should not be very acidic. Scotch bright it on wearing long sleeves and pants(it should be mild enough to not hurt if it contacts your skin), rinse it off before it dries with plain water. Dry everything thoroughly then brush on your alodine and rinse off the excess with plain water before it dries. May need several people with brushes to coat the whole thing before it starts to dry. Otherwise do it in sections, making sure it is completely dry of water before starting another section. After alodining is done, apply epoxy primer and topcoat according to paint manufactures recommendations. I would recommend using epoxy primer and top coat from the same manufacturer instead of mixing different brands. DP-40 epoxy primer and Concept topcoat from PPG is a very durable easy to use system in my opinion. It also is readily available at many auto parts suppliers. Polyfiber makes a great epoxy primer called epibond and topcoat called Aerothane another good system, but harder to get and you may have to have it shipped. Other manufactures make some pretty good systems as well. I have heard that DuPont has some sort of primer that does the conversion coating as well. I am not familiar with it. Not to be confused with etch primers. I would stay away from these, because they are not very durable like epoxy and cannot be top coated with epoxy primer.
That's my 2 cents worth of opinion
Tom