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PurpleZL1
07-03-2012, 02:54 PM
I assembled this checklist from a lot of different sources, and interviews, after I could not find anything online here that covers it. Please let me know your thoughts and suggestions.

Assumptions: You are using chemicals per the chemical manufacturer’s safety and handling instructions.
DuPont Technical Page (http://pc.dupont.com/dpc/en/US/html/visitor/b/avi/s/product/avi_tech.html) Sherwin-Williams (http://www.swaerospace.com/products/brands/jet-glo/)

Remove the paint:
Thoroughly wash the plane with a wax free soap, especially landing gear and other areas which may have grease or oil residue. This will improve the performance of the strippers.
Remove:

Control surfaces
Inspection panels
Fairings
Moldings
Bag and mark the fasteners so you know which type went where later- even if you are replacing them. I like to take cell phone photos of everything during disassembly.

Cover windows with aluminum foil and edge with foil tape. Extend the foil tape 3/8” past covered area onto the metal airframe. This edge will be stripped separately later.

Also cover with foil and foil tape:

Plastic, Fiberglass and composite (not removed in step 2)
Boots
Antennas
All openings into aircraft such as door seams (¾ inch aluminum foil tape). Can’t emphasize this enough – you don’t want stripper inside your airplane which will work its way out later so even cover small openings including where the inspection panels were removed.
Thin strips over the wing/fuselage gasket (Piper).

Wet the shop floor and cover with plastic polyethylene drop cloths ( if compatible with your choice of stripper) - so you can recover waste. Apply the stripper and cover with polyethylene drop cloths ( if compatible with your stripper) to prevent it drying out early - the polyethylene can make the stripper last indefinitely depending how well you seal it. After checking a test spot, scrub paint loose with stiff 12”-14” broom, re-apply more stripper, then pressure wash – don’t spare time or water on this step. Don’t use too narrow a pressure washer orifice - it will be easy to damage thin components.
Remove remaining paint and corrosion from the following parts:

Rivet lines
Seams
All edges that were covered with the foil tape.
Important – do not use steel wire brushes or scrapers because the steel particles will embed in the aluminum promoting corrosion. You can use non-steel abrasive pads.

Perform Airframe inspection by A&P for corrosion or underlying damage to aircraft.
Treat the metal:
Acid Etch process with an aluminum cleaner to guarantee that all residue has been removed (Dupont 13204S or 13205S as examples) and rinse with water. (From Bill Berson) The phosphoric acid etch improves paint adhesion by cleaning away oil. It should be applied with a weed sprayer and scrubbed well with scotchbrite. This is the most important step in paint adhesion because the acid scrub and rinse removes the oil/wax. Beaded water indicates oil, keep scrubbing with etch until the water flows flat. This is called the water break test in the composite industry (works for paint adhesion also) The self-etch primer without acid scrub will not provide this.
Alodine (chromic acid) is applied (such as DuPont 13206S Aluminum Conversion Coating solution) , left on until color change is evident, and rinsed off with fresh water and then dry overnight. (Note - you must not let the Alodine dry on the plane)
Dupont recommends priming as soon as possible after this coating as been applied, no more than 36 hours or it should be reapplied.
Wear plastic gloves from this point forward if you haven’t already; oil from your skin is bad for paint adhesion.
Perform Airframe inspection by A&P.
Fix problems:
Clean plane with MEK or similar.
Mask as necessary with paper and masking tape. Mask any opening – blowing paint into the wing is sloppy.
Wet down the floor to eliminate possible air contamination caused by paint technician movement across the floor during the paint process.
Coat with epoxy primer to provide corrosion resistance and paint adhesion. The paint must be applied soon or the primer must be lightly sanded. Check paint manufacturer specs. Sherwin-Williams recommends a minimum setup time of 12 hours before top coat is applied and a maximum of 36 hours. After that scuffing is required for paint adhesion.
Sand fiberglass/plastic panels removed or masked earlier – anything not stripped. I like to finish with 400 and then 600 grit wet paper by hand after 220 machine sanding.
Use body filler to fill small blemishes in the airframe, sand smooth. Check out Sherwin Williams Fill Bond (http://www.alliancecoatings.com/fill-bond-video.php)
Apply fill primer (sandable high-build epoxy primer such as SW CM0560566) as needed and sparingly - mask off panels not needing fill primer.
Sand fill primer coat - again with 400 and then 600 grit wet paper by hand after 220 machine sanding.
Paint:
Once you begin, from this point forward, the clock is ticking. Steps 2 – 8 should be done in the same working day for best results.
Primer was applied minimum 12 hours prior and no more than 36 or scuffing is required. Check primer/paint data sheets.
Clean plane thoroughly. Sanding dust blown out of small pockets has ruined many paint jobs.
Mask as necessary with paper and masking tape. Mask any opening – blowing paint into the wing is sloppy.
Wet down the floor to eliminate possible air contamination caused by paint technician movement across the floor during the paint process.
Coat with two coats of high gloss polyurethane. Start with the lower surfaces of the plane and work up.
Color stripes are added after appropriate drying time, but not too long after. Check paint manufacturer specs.
Remove tape as soon as possible while the edges are still soft. Leaving it too long can imprint paint below (for striping) and could tear/chip paint edges when removed.
Reassemble control surfaces, cowling, etc. with new stainless steel screws as appropriate – consider nylon backing washers where possible. Avoid painting any fastener that will be frequently removed such as cowl fasteners.
Factory-designated equipment and specifications are used to balance all control surfaces by A&P.
Inspect your aircraft, and make logbook entries.
Replace existing placards with new placards in accordance with FAA requirements.

Bill Berson
07-03-2012, 04:28 PM
That's quite a detailed checklist, here is my single comment:

I never used any fill primer on a metal airplane yet, seems to me just added weight and cost. But if you do use fill primer (what is it?) then shouldn't it go on top of the epoxy coat to smooth the epoxy? The epoxy primer should be the first coat.

PurpleZL1
07-03-2012, 06:16 PM
Thanks - That's why I posted the checklist. I found the fill primer note on a painter's website. They used high solids sandable primer in areas needing work such as hail dents and followed it up after the work with the epoxy primer just before painting. I noticed Dupont recommends full primer coats right after the Alodine and they also recommend no more than 36 hours between painting the epoxy primer the color coats. That would mean you would need to work really quick or face sanding the epoxy primer after the 36 hour mark. :(

WLIU
07-05-2012, 05:45 AM
All of the paint manufacturers instruct that after the primer is applied, the paint should be applied within a time limit or you need to sand for best adhesion.

Best of luck,

Wes
N78PS

PurpleZL1
07-05-2012, 07:44 AM
Thanks - I updated the post - in blue - moving the epoxy primer to be applied first to the entire plane and then a sandable primer over that (per Sherwin-Williams) in areas that need it. I have some very light hail dents so I will probably apply the sandable primer to the top of my wing and some body filler.

Anyone know where we can buy commercial aircraft stripper? I heard "Aircraft" strippers have corrosion control properties not found in other strippers.

WLIU
07-05-2012, 09:07 AM
Aircraft stripper - I think that I have seen it at Pep Boys. Your local auto paint supplier will likely stock it. Airplanes and custom autos are really the applications for a quality paint remover. I will note that I am told that not all brands of stripper are effective with all types of paint. I think that I read that Sherwin-Williams might actually make a really good stripper that attacks polyurethane effectively.

The paint stripper that you find in Home Depot and Lowes is really targetted at furniture refinishers and applications like metal house trim items.

If you are removing the paint from an entire airplane, be aware of the environmental concerns. I understand that there are now paint removers that are environmentally friendly, but I do not have experience with them. What you do not want is to have your hangar designated a sire requiring formal environmental cleanup.

Best of luck,

Wes
N78PS

PurpleZL1
07-05-2012, 10:09 AM
Actually the strippers found in retail stores are not ideal for large projects like this. PPG has a product called Eldorado PR-2002 (http://www.ppg.com/coatings/aerospace/coatings/coatingsproducts/Documents/PR_2002_Paint_Remover.pdf), and there are many others, but I can't find anyone who will sell them to an individual - so far. I have stripped several vehicles with retail products and they are too much work.

martymayes
07-05-2012, 10:15 AM
- Anyone know where we can buy commercial aircraft stripper? I heard "Aircraft" strippers have corrosion control properties not found in other strippers.

Turco makes a full line of aviation stripper/coating poducts. Methylene chloride, low odor and water based, just name yur poison. They have epoxy stippers, polyurethane strippers, stippers for aluminum, magnesuim, etc. They also make alkaline cleaners for cleaning the stripper off and getting the grime out of wheel wells and engine compartments. If you want one stop shopping you can buy your alodyne, conversion coatings, corrosion removers, etc. from the same Turco dealer. You can buy all that online at Graco or equivalent but watch out for hazmat shipping. I'd try and find a local dealer.

FWIW, anyone can put goop in a bottle and call it "aircraft stripper" ....doesn't mean it's a product you should use on your plane.

Pearson
07-05-2012, 11:37 AM
Purple,

I think someone gave you some bad info. Your checklist is filled with instructions for a disaster. Below is a list of things I see that are disasters looking for a place to happen. There is no such thing as “painters plastic”, at least not in regards to painting an airplane.

If you cover your shop floor with plastic sheet, the stripper will drip down onto it and make a huge mess when it melts the plastic.

I am not sure why you would cover the windows with “painters plastic” and then cover that with aluminum foil. Just use aluminum foil.

If you cover the stripper with plastic drop cloths, it will melt the plastic into a gooey mess. A broom will not scrub the softened paint off. Use a plastic bondo spreader, or a small piece of aluminum sheet. You CAN use a steel wide blade putty knife. Just don’t press into the aluminum very hard.

At one point you mention what Dupont recommends for priming. Later you mention Sherwin Williams. It is best to decide what brand you are going to use and follow that manufacturer’s recommendations and directions. What works for one brand may not work for another.

If you have hail dents, fill them with body filler and after sanding it smooth, THEN put sandable primer over it. Don't but body filler on top of primer.

You mention that the color stripes are added when the paint has cured for a certain time. It is best to paint the color stripes FIRST. After that paint is dry, you mask it off and shoot the rest of the plane. Then when you remove the masking over the stripe color and there is your stripe.

You also mention removing tapes as soon as possible while the paint is still soft. This will lead to a very ragged edge. It is best to let the paint dry thoroughly before removing the tape. About 24 hours is usually a good time. Spend the money for 3M "Fine Line" tape.


Before you spend many hundreds of dollars on stripper and make a big mess, get some 280 or 320 grit "wet or dry" sand paper. Fill a bucket with water and see how quickly you can water sand a one foot square down to the aluminum. Don't sand over rivets unless they are counter sunk. Notice how long it takes you to do a one foot square. Then use stripper to do a one foot square. Include in the time for the stripper the amount of time you spend cleaning the shop floor and power washing the stripper out of the seams on your plane. Make sure you keep the hangar well ventilated when using the stripper.

PurpleZL1
07-05-2012, 12:45 PM
Thanks Pearson - I think the plastic drops cloth will depend on which stripper you use? Most of my information was gleaned from various paint shop sites, all who say they use newer EPA friendly chemicals - noted most showing the process without a mask. Good point - I will update the list to check compatibility.

Bondo over bare aluminum? Would like more clarification on that, I would think there should be something under the bondo to prevent corrosion? I painted a few trucks when I was a kid and it was not unusual to find corrosion under old bondo on the aluminum cabs. It looks like commercial shop practice is to not sand aluminum skin and since it's pretty thin to start with that may be why.

Stripe painting before or after is probably a personal call. If you paint them first, you must deal with dust over the greater part of the plane while the stripes dry. Again, on the commercial sites they almost universally paint the plane white, wait (per the label instructions) tape, and paint stripes.


http://www.arizonaaircraftpainting.com/new/wp-content/gallery/bonanza-f33a/100_5862.jpg

Bill Berson
07-05-2012, 04:02 PM
In my airplane paint shop, we always put the bondo on bare aluminum (no primer but after alodined). Mostly because it is the fastest and easiest way for a production shop. Otherwise the sanding will go through primer anyway and need more work.
The finished bondo area could use some extra spot primer coats first, then prime the whole thing.

When young, I worked in an airplane paint shop that never used primer at all, just etched and alodined the stripped aluminum and coated directly with white Imron paint. This saves weight, cost, time, and is much smoother than primer. Makes it easier to strip later also. A working commercial plane gets scratched more than corrodes on the external skin and a new paint job every 5 years is needed anyway. Maybe 10 years, if treated well.
I think only float planes need primer, but it is your call.

WLIU
07-06-2012, 05:45 AM
If I understand correctly, the traditional acid etch and alodine process can be environmentally problematical. Modern paint manufacturers specify a self-etching primer for best paint adhesion. Ease of future stripping is a negative attribute, not a positive one. Modern paints are supposed to be hard to take off....

Best of luck,

Wes
N78PS

Bill Berson
07-06-2012, 08:57 AM
The phosphoric acid etch improves paint adhesion by cleaning away oil. It should be applied with a weed sprayer and scrubbed well with scotchbrite. This is the most important step in paint adhesion because the acid scrub and rinse removes the oil/wax. Beaded water indicates oil, keep scrubbing with etch until the water flows flat. This is called the water break test in the composite industry (works for paint adhesion also) The self-etch primer without acid scrub will not provide this.
Skip the alodine if you can't deal with the waste disposal and consider the self- etch primer. But don't skip the phosphoric acid. I don't think phosphoric acid is harmful to the environment.

Lear Jets need more adhesion than a Sonex. The more coats, the more stripper required to remove. Again, it's your call, but I guarantee the paint salesman will insist you go with the most expensive process.

PurpleZL1
07-06-2012, 11:30 AM
Turco makes a full line of aviation stripper/coating poducts. Methylene chloride, low odor and water based, just name yur poison. They have epoxy stippers, polyurethane strippers, stippers for aluminum, magnesuim, etc. They also make alkaline cleaners for cleaning the stripper off and getting the grime out of wheel wells and engine compartments. If you want one stop shopping you can buy your alodyne, conversion coatings, corrosion removers, etc. from the same Turco dealer. You can buy all that online at Graco or equivalent but watch out for hazmat shipping. I'd try and find a local dealer.

FWIW, anyone can put goop in a bottle and call it "aircraft stripper" ....doesn't mean it's a product you should use on your plane.

Some strippers: (will five gallons do a Cherokee 140 with only one very thin paint job?)

EFS-2500 (http://www.m-tc.com/f_index.php) by Molecular-Tech Coatings in Canada and distributed here by Graco - in stock. It runs about $280 for five gallons and sample not available.
Oxystrip 2030 Pro (http://www.removepaints.com/Products/OxyStrip_2030Pro.aspx) by General Chemical is $32.25 a gallon, water based, and I have ordered a quart to test. Less expensive, but it may take more.
SPC-909 by AkzoNobe (http://www.aerocolorspaints.com/paintremovers.htm)l (http://www.aerocolorspaints.com/data/AkzoNobel_SPC-909.pdf) looks promising. Graco $362 for five gallons. Non-stock and 4 weeks.
Turco 5351 is the old Methylene chloride paint stripper and it's $403 and non-stock at Graco.
Also,

PPG only sells to pros apparently.
After I get some samples I will do some tests and report back with photos.


Updated 7/16/12

Dad's Easy Spray Contractor Grade (http://www.dadseasyspray.com/contractor-grade). I tried the regular Dad's last weekend alongside the Oxystrip and while the Oxystrip had no odor and seems to be skin friendly it was slow and difficult to keep mixed. The Dad's is thin enough to spray with a garden pumper (Viton required) but thickens on contact and takes the paint off pretty good. I just noticed they make a "contractor grade" of the same stuff and I will try that as soon as the order arrives.

In this picture the white was already scraped off with a plastic tool and the red, which was a stripe over the white, needed more time. The plastic kept the stripper wet indefinitely - or at least for a couple of hours. I took off about 10 sq. ft. of paint with a quart.

2267

Bill Berson
07-06-2012, 12:38 PM
Amount of stripper depends on the paint type and thickness and skill of worker. Many Cherokees were factory coated with lacquer. This will melt rather than lift, and worse, water makes it solid again. So additional coats of stripper work best without water, try to squeegee it off before using water for the last bits.

Most singles need about 20-30 gallons, I seem to recall. It all depends.

PurpleZL1
07-06-2012, 01:10 PM
This one was stripped and painted at a shop in Alabama in 2003. There are chipped areas all over the place and the white paint is faded. I bought it in 2008 and the paint was trashed then (I keep it inside) but the paint comes off so easy I figure the stripper will have an easy time. It's a shame the $10,000 paint job didn't last any longer than it did.

Bill Berson
07-06-2012, 03:22 PM
I see you have confirmed my comment that a paint job usually lasts about 5 years (2003-2008 in your case).
It hardly helps to spend $10,000, in my opinion.

Proper surface cleaning is most important (post #13) and should make the paint last 10 years. But even Imron will have fading and some cracks at 10 years. Airplanes flex. Not much can be done other than repaint.

Pearson
07-06-2012, 04:22 PM
If you use Imron to paint your airplane, you will be lucky if it stays attached for five years. Imron is very brittle. I would never use it to paint an airplane. Air Tech Coatings and Polyfiber both make a great urethane paint that will flex. Because it is flexible, it doesn't flake off like a more brittle paint. Of the two, I prefer Air Tech Coatings because it seems to flow out better. The Poly Fiber is great, but I seem to get more orange peel with it than the Air Tech Coatings finish.

If you are doing a plane as small as a Cherokee 140, I would just water sand it down rather than mess with chemical strippers. You can use a scotch brite bad over the rivets. It is almost as quick as chemical stripping and much quicker clean up. It is also cheaper.

WLIU
07-08-2012, 07:35 AM
Uh, properly applied Imron is NOT brittle. I have one airplane that was painted with Imron in the early '80's that still looks great and is not chipped. I have another airplane that was painted with Imron in the early '90's and also still looks great despite being parked outside in New England for most of its life. I don't baby the airplanes either.

If your paint is only lasting 5 years you need to patronize a better shop.

Sanding the finish off an airplane is an exercise for a real masochist. I have sanded a lot of paint and it helps keep my upper body in shape. If you don't have lots of spare time and need "wax on - wax off" to be part of your conditioning and weight loss program, I recommend a good chemical stripper to remove your paint.

Preparation is everything with paint, so once you have the airplane stripped, do spend a lot of quality time with a good cleaner, scotchbrite, and a good self-etching primer. And follow the directions for the paint exactly as printed.

Best of luck,

Wes

PurpleZL1
07-09-2012, 06:56 AM
When in doubt - TEST



If you cover your shop floor with plastic sheet, the stripper will drip down onto it and make a huge mess when it melts the plastic. I am not sure why you would cover the windows with “painters plastic” and then cover that with aluminum foil. Just use aluminum foil.
If you cover the stripper with plastic drop cloths, it will melt the plastic into a gooey mess.


In ASA's Airframe Volume 1: Structures, by Dale Crane (which I believe anyone working on their own airplane should read - big help to me anyway), on page 212: ".. apply a heavy coat of stripper with a bristle brush or a nonatomizing spray, and cover it with polyethylene sheeting to prevent it evaporating before it does it work."

What you said made sense to me because this stuff is so caustic and a long time ago I literally melted a tail light on a car with paint stripper. However, it appears polyethylene plastic does not mind the stripper at all. To test this I poured hardware store stripper (http://www.dadseasyspray.com) into a polyethylene sandwich bag and left it overnight - no problems - see pic below.
2172

PurpleZL1
07-09-2012, 07:00 AM
If I painted over the old paint I would still have the adhesion problems between the old paint and the aluminum. I have had pretty good luck with Imron myself on my jetboat which has had a tough life on Texoma the last 15 years - talk about flex! Thanks guys.

Updated the list with most of everyone's comments.