Corrosion protection and the use of primers are topics with as many opinions as there are builders. Here are some tips submitted by our members.
Deft Primer Info: In the for what it’s worth department, I’ve been in touch with the Deft Co. in search of their spray-gun cleaner, IS-248 (formerly IS-221). No one has it locally, SH does not handle it, and Deft will sell it in $250 orders only. Not to worry. Deft tech department advises that IS-248 is nothing more than equal parts alcohol (any kind: isopropyl, methyl, ethyl, Smirnoff’s probably) and either toluene or xylene. One-to-one ratio. And, actually, one can substitute SC100 Solvent (a more environmentally friendly substance) for the toluene or xylene. I haven’t been able to find the SC 100 Solvent so plan to use Isopropyl alcohol and xylene. While on the phone with the Deft tech rep , I told him I’d heard that maybe it wasn’t a good idea to use Alodine after washing with DX-532 and before spraying with the Deft BAC-452. Tech rep, Leon-extremely helpful– said it is very important that Alodine be applied properly: during wash-off, there must be no water breaks (little circles-water spots). The piece must be allowed to dry completely and BAC-452 must be used within 24 hours. If there is a problem applying Alodine correctly, per the foregoing, it will be better not to use it at all and go straight from the wash to the BAC-452 primer, only instead of using the DX-532 wash in this case, use MEK as the wash. Other tidbit I gleaned from Leon was that in using the Alodine 503 (the pigmented alternative to the clear DX-501), a good application will result in a nice, light golden color, not too dark. Well, I have not yet tried any of this but will shortly as soon as the xylene comes in from the local paint store. In the meantime, I bought an cheap laundry/utility tub, attached a flexible drain hose, put it out in the woods along with the garden hose and plan to use this setup as a wash and Alodine station.
–Monty Rogers
Primer: I have researched the primer that S/H recommends and found it to be superior to all others on the market. If anyone needs tips on using this primer, feel free to communicate.I would like to elaboraate concerning the deft 44GN11 primer. I have talked extensively to the tech representative at Deft and have acquired considerable information. This is the same primer that Boeing is using on the new 777 planes and was specially formulated for boeing for this project. Boeing instructed Deft that this primer should exceed MIL-P-23377E type 1class 1 (which is the Mil Spec for us paint primer S9001). This includes submersion in hot hydraulic fluid for extended period of time. Clean up tip: It is possible to clean up all equipment after mixing and or spraying with virtually no thinner by using high pressure water from your garden hose applied to the equipment immediately after mixing or spraying with your equipment (believe me this works!)
Deft Primer Discoloration: I have talked to the technical representatives in depth in the past and the only color distortions that you could experience are from a high humidity environment. This represents itself in a brownish green blotching which is caused by the chromium coming to the surface. This does not affect the quality of the finished product just the appearance. The primer on the pre finished spars does not seem to me to be Deft 44 gn 11
Another tip from tech in a high humidity environment ( raining outside ) if you place a fan blowing on the parts to aid in evaporation of the water this will prevent the above mentioned blotching. Another tip from tech much to my surprise they do not recommend alodine. Surface prep should include degreasing and ScotchBrite scrubbing with Alumaprep followed immediately ( before oxidation begins ) with Primer. I have just received a new batch of Primer so if anyone is interested purchasing any kits please see Options for details. Also if there is any interest for smaller quantities other than 1 gallon kits (half gallon kits) let me know.
–Dan White
Priming parts: When preparing parts for primer spraying, I have found that considerable time can be saved if all the small parts are lashed to a frame. I have tried a few different frames and attachments but my latest attempt worked best. I used some 1x4s from the wing crates and screwed together a rectangular frame. On the frame, I attached 2″ mesh chicken wire with a staple gun. All of my flap ribs, doublers,aileron hinge parts, and aileron bellcrank parts (almost 100 individual pieces!) were attached to the mesh with strands of floral wire (thin, pliable wire used in floral arrangements). After everything was attached, it a simple matter of spraying the primer on. This was by far the simplest arrangement I have found for spraying a bunch of little parts.
–Lee Clements
Acid etching/Alodine: For doing the acid etch/alodine thing, I built a table out of the tail kit crate. Result is a 32″ X 75″ surface which is big enough for all but the largest sheets. Top is inset and sloped toward a drain in one corner which is over my basement drain. Painted the top with hardware store “epoxy” paint Just used a hose for flushing the parts.
–Dennis Brush
More on DEFT: Continuing to be concerned with the looks of the Deft that I applied to my GlaStar tail feathers, I called Deft Corp. in Irvine CA and talked to Leon Ewald, in the tech shop for Aircraft coatings. Their Phone number is 714-476-6747, and he told me to call anytime I have ANY questions. I found the following.
The light green colored Deft and the gray colored (when applied) is actually the same product, except for weight. The green has more pigment in it and weighs more. The gray has aluminum flake which gives it the light gray color and keeps the weight down, and the aluminum is only put in to cover the surface as without it you wouldn’t be able to tell it was on the surface.They DO NOT RECOMMEND acid wash and alodine (If you question this, call them at the above number). They said if the alodine was not properly applied, it could affect the way the Deft sticks and could mess up the entire job. They said all that was needed was an MEK wash, and to wipe down the parts with a WHITE cloth and MEK just prior to application of Deft. Use white cloth to prevent color residue from the colored cloth contaminating the surface. The white cloth also shows any signs of dirt or other contamination that might be on the surface. Be sure NO FINGERPRINTS are on the surface
Deft should be put on at a thickness of .5 to .9 mil and let air dry minimum of 12 hours to set, 7 days for full cure. This is an epoxy-polyamid material and should be applied in one pass. He said it is proper if the surface is JUST barely completely dampened. Any more does no good, and just adds weight.
I feel much better now that I know, I just happened to hit it with 2 passes, which added about 3 times more Deft than was needed. The best part though, is no acid etch or alodine. Just thought you might like to know.
–Art Fish #5289
Avoiding painting clecos when corrosion protecting: To prevent spraying clecos when corrosion proofing I cut ordinary 1/2 ” garden hose into 2 1/2″ lengths (approximately 100). These short pieces fit neatly like a glove over the top of clecos.
–Frank Miskelly #5577
8/28/98 Skin prep: While acid washing my first few skins I became aware that the Alclad required little treatment. The manufacturer’s heavy ink markings, on the other hand, necessitated lots of rubbing with ScotchBrite and/or a lengthy acid soak. A rather scuffed surface resulted. I found an easier method where I wipe off the ink with a cloth and a little MEK before applying the cleaner. Takes half a minute per skin.
–Bruce McGregor #5368
8/29/99 Deft Priming Primer
Firstly, DO IT! It is money in the bank. Primer coating will preserve the aircraft while you own it and it will be worth more money in your pocket when you sell it some day. Priming an aircraft that is already built is impossible because you cannot spray primer between assembled parts.
Calling this coating “PRIMER” is a misnomer, especially as it is used as the final coating on our interior aircraft parts.
We’ll discuss the type that SHAI sells with the kit, which is made by Deft®. This was developed for the Boeing 777 program. If it is right for Boeing to use, it has to be good. Airliner primer will last practically forever and will resist just about everything you can attack it with except sandpaper.
How to mix the primer. You can’t go wrong with the directions that SHAH sends with it. You will think you are mixing exotic rocket fuel. (Safety check: do you have your latex or vinyl gloves on?) By the time you finish your aircraft’s metal work, you will be throwing it together with abandon.
First tip- the mixing container is too big for anything but very large batches. If you use the measure marks on the container, you will throw a lot of it away. Get a plastic quart container at your paint store. Get one with lots of division markings. This makes it easy to make smaller batches.
Ok! So let’s mix. First order of the day is to get your stir stick and thoroughly mix the thick can. It tends to settle out on the bottom. This takes a lot of heavy stirring the first time around. Next decide on the size of the batch. If your new container has lots of equal measure lines, the smallest batch you can mix is to pour two segments of the heavy Deft base material and then add one segment of the liquid catalyst. Now you have established the desired 2 to 1 ratio. Next add water. Most any water will thin it but the dry finish will contain whatever impurities that the water contains so pure distilled water is the best bet.
Next, the directions say measure and stir, measure and stir and they mention five minutes for each cycle. Remember that this is an epoxy and it requires a lot of mixing. Putting the mix into a clean glass jar with a lid and shaking works well.
To tweak the final consistency, I will guarantee that by the time you finish your metal work you will be into the pour and stir thoroughly mode and you will add enough water to get whatever spray thickness works well. After awhile, you can look at the way it runs off the stir stick to judge the right amount of thinning. If you want to brush on a little, dip out a bit before it is thinned to spraying consistency.
Keep your batch covered. This and stirring frequently will keep it from “skinning over” on the surface. Need a quick cover? A piece of flat metal will do if one is lying around. However a workable cover is a wet rag or a folded and wet paper towel. . This and stirring frequently will keep it from “skinning over” on the surface. Need a quick cover? A piece of flat metal will do if one is lying around. However a workable cover is a wet rag or a folded and wet paper towel.
Adjust your spray gun. Fill the spray can with water and adjust the gun for the pattern, air flow and primer flow. This will not be exactly right for the thicker primer but you will know just what to tweak by then. Fill the spray can with water and adjust the gun for the pattern, air flow and primer flow. This will not be exactly right for the thicker primer but you will know just what to tweak by then.
Pour your primer through a strainer and into your gun’s cup. If you do not strain it, sooner or later you will wish you had.
Wear old clothing. You will get spots on them no matter how hard you try not to. If you want to remove spots, do it quickly by flushing with water before they dry. Once set, the spots will still be there when the Goodwill people get them.
Wear a good respirator certified for epoxy paint use! This is an epoxy and priming your lungs can ruin your whole day. Even if you do it outside with a breeze blowing, you will inhale some and you will cough the rest of the day. Now, how do you suppose I know that???
How about metal prep? We used ScotchBrite pads, acid etch and alodine. Again, it might be overkill but SHAI recommends it and it sure can not hurt. We used ScotchBrite pads, acid etch and alodine. Again, it might be overkill but SHAI recommends it and it sure can not hurt.
How thick should the coating be? Well! Do not just use a “dust coat”. This is the final finish and you do not want it so porous that the metal is not fully protected. Zinc Chromate was supposed to be a dust coat, if you were going to spray on a finish coat. The Zinc Chromate gripped the metal and the finish coat gripped the porous Zinc Chromate. Forget about dust coats for this application. Well! Do not just use a “dust coat”. This is the final finish and you do not want it so porous that the metal is not fully protected. Zinc Chromate was supposed to be a dust coat, if you were going to spray on a finish coat. The Zinc Chromate gripped the metal and the finish coat gripped the porous Zinc Chromate. Forget about dust coats for this application.
You will have to use some judgement of your own. One way to get an idea is to spray over some printing on the metal. You should coat it enough that the printing will disappear. Of course you want all the printing cleaned off but this is just for a test.
The directions advise several light coats. I use at least two, one each direction (cross-coats at 90 degrees). Then, if you detect thin areas, do a bit more. Putting too much on at once will cause runs. Keep the metal as flat if possible and that will cut down on runs. Runs will dry hard enough to keep fitted parts separated and will have to be sanded off before assembly.
What to spray. We are spraying or brushing everything we can get at. Our plane will eventually be on floats. That and being near the salty ocean make it really needed. However, even if it is assembled in the desert, planes fly and who knows where it will end up at. Primer-coat it while it is easy. One way or another, it will be dollars in your pocket. We are spraying or brushing everything we can get at. Our plane will eventually be on floats. That and being near the salty ocean make it really needed. However, even if it is assembled in the desert, planes fly and who knows where it will end up at. Primer-coat it while it is easy. One way or another, it will be dollars in your pocket.
Special areas to consider. When you counter sink your spars you produce a lot of bare metal even if your jump start spar is already primed. We resprayed the spar flange with a light coat of primer. A builder I know used a Q-Tip and treated each hole. I heard some one say “that is overkill”. In my book, bare metal is bare metal and if it is part of the spar, it is important bare metal. . When you counter sink your spars you produce a lot of bare metal even if your jump start spar is already primed. We resprayed the spar flange with a light coat of primer. A builder I know used a Q-Tip and treated each hole. I heard some one say “that is overkill”. In my book, bare metal is bare metal and if it is part of the spar, it is important bare metal.
Wherever metal is put together or over lapped, both parts should be primed. Moisture loves to get between metal and go to work. One very important metal overlap (or double metal in this case) is the 18 inch wide reinforcement plate on the inboard lower skin. Be sure both inner surfaces have a very perfect coat of primer. If not the moisture that is bound to get in there will corrode the sheets of metal and reduce their strength at the same time. The really bad part is that this corrosion cannot be seen from inside of the wing or from the outside. You will never know how bad it is until it eats clear through the skin. Of course, the original builder will probably never own the plane long enough for this to be his problem, but some day it could be someone else’s problem. Do that someone a favor and spend the extra few minutes to coat these areas well.
Cherry rivets. We dipped the barrel of each one in primer before we pulled them. This puts primer on the barrel, the bottom pull stem and as you place it in the hole, a little ends up under the head. Overkill? Well maybe but we felt good doing it. One thing that is a must, “not overkill” is to seal the outside stem area with a drop or two of primer to keep moisture out of the stem and/or cavity , depending on where the stem snaps off. We dipped the barrel of each one in primer before we pulled them. This puts primer on the barrel, the bottom pull stem and as you place it in the hole, a little ends up under the head. Overkill? Well maybe but we felt good doing it. One thing that is a must, “not overkill” is to seal the outside stem area with a drop or two of primer to keep moisture out of the stem and/or cavity , depending on where the stem snaps off.
A cheap and tiny artists brush is good for the above job. Just grasping the handle works ok. However, I like to bend the tip 45 degrees or 90, depending on the job and reinforce the bend area with a little masking tape. Then take a length of 1/4″ copper tube and slide it over the brush handle and tape it in place. Now dip and drip. You will find it easier to get into places that a straight handle will not do easily. Also, on flat surfaces, such as treating cherry rivet stems, two hands will give pin point accuracy for the drip.
Making tiny batches of Deft primer. Steal from the spouse or buy three cheap teaspoons and three tablespoons. Use either teaspoons or tablespoons, depending on the size of the batch needed. Stir the base as before and, using the stir stick, drip a spoon level full and drop it into your container. A nice glass or plastic measuring cup is a good size. Do this again with the second spoon. Dip a level spoon of catalyst and pour it into the cup. Add water and do a two spoon stir until thin enough to scrape off one spoon and finish stirring with the other. Likely you will be brushing a small batch so do not get it too thin. Steal from the spouse or buy three cheap teaspoons and three tablespoons. Use either teaspoons or tablespoons, depending on the size of the batch needed. Stir the base as before and, using the stir stick, drip a spoon level full and drop it into your container. A nice glass or plastic measuring cup is a good size. Do this again with the second spoon. Dip a level spoon of catalyst and pour it into the cup. Add water and do a two spoon stir until thin enough to scrape off one spoon and finish stirring with the other. Likely you will be brushing a small batch so do not get it too thin.
A handy and tiny container to brush out of. Get a plastic spray can cap. Cut the outer skirt partly away and spoon primer into the center cup. It’s just the right size and will not tip over. You may partially cover the cup with tape to cut down on air that skins up the surface. Get a plastic spray can cap. Cut the outer skirt partly away and spoon primer into the center cup. It’s just the right size and will not tip over. You may partially cover the cup with tape to cut down on air that skins up the surface.
If you primer is fresh and hasn’t been stored by SHAI for too long, and you do it right after you mix it, you can freeze it and use it next day. However as the basic batch gets older, this will not work.
How do you know if your basic batch is getting too old? Well! If you mix it and 30 minutes later it will not spray you, will know it is getting pretty aged.
Cleanup. Run lots of water through your gun and finish with Deft® solvent. Want an inexpensive version? Mix a 50-50 batch of Toluol (Toluene) and Alcohol. This is the only thing that works. Don’t try MEK, Acetone, or anything else. As usual, wear heavy duty nitrite or butyl rubber gloves.
–Orville Eliason
Tray – Corrosion Proofing – A very effective tray in which to soak ribs and other “short” brackets in Alumiprep and Alodine is a watering pan used for wallpapering. They measure about 6″ wide, 4″ deep and roughly 36″ long and are made of polyethylene. Cost at the store is less than $10, and its shape allows for a relatively deep fluid level with only about a half gallon.
–Mark Neubauer
More on DEFT Primer – I just spoke with Leon Ewald at Deft (949-476-6747) in an attempt to decide how to prep the aluminum prior to priming (which cleaners, whether to alodine, etc.). He was extremely knowledgeable, friendly, and helpful, and here’s a brief summary of what I learned (essentially a repeat of earlier builder’s tips, with a little more amplification). This is the same guy who advises aerospace companies such as Boeing (a Deft user) on how to use the Deft products.
Alodine has no appreciable benefit on the INTERNAL structure, or on the EXTERNAL structure unless the latter is routinely and consistently exposed to a harsh environment (salt water, extremes of temperature and humidity). Living near salt water in the Puget Sound region, as I do, with plans for eventual saltwater float flying in my GlaStar, Leon recommended alodining the entire external surface, if possible (followed by Deft primer and good paint), but if I could do only the floats (if aluminum) and other areas that were routinely drenched with saltwater, that would be acceptable. He saw no point whatsoever in alodining any of the interior structure, even for saltwater float flying, feeling that any saltwater finding its way inside would be easily handled by the non-alodined Deft (with the possible exception of aluminum floats). It’s only for extreme and prolonged exposure that alodining can improve the longevity of the Deft primer.
In no cases should alodine by applied unless the user has the facilities for completely soaking the pieces for several minutes, and COMPLETELY rinsing off ALL residue before priming. Failure to do so will compromise the Deft priming, and the entire coating will be at risk of early failure, from the inside out. Properly alodining large pieces, such as wing skins, could be a real problem.
For initial cleaning and preparation of aluminum that will not be alodined, MEK is superior, period. It produces the most consistently best surface and the longest-lasting, most reliable corrosion protection from the Deft primer. MEK is recommended even if it requires the use of extraordinary safety measures, since it is very flammable and very toxic. An acceptable alternative for preparing the surface prior to priming is MIL-T-81772 Type II epoxy reducer (available at industrial paint supply houses such as Sherwin Williams, at a cost comparable to MEK — Type II is important, don’t get Type I). Although not quite as suitable as MEK, it is potentially less harmful (I don’t know the particulars). Other types of products (e.g., Alumaprep) are NOT recommended before priming when alodine will not be used.
BTW, Leon pronounced it “allo-deen”, I’ve always assumed “allo-dine”.
–Don McCall #5688
DEFT Use: The advice from Deft parallels my own experience. I used acetone to degrease (chemically very similar to MEK and I had a gallon of it anyway!) and then scrubbed with Scotchbrite and TSP (trisodium phosphate @ 1 cup/gallon) and a squirt of washing up liquid (important) and rinsed very well under the tap. I looked for a water-break free surface at this point when rinsing. I then allowed the parts to dry (on my $10.90 wooden laundry rack from Target) and finally sprayed with the Deft using a $39.90 HVLP spray gun from Harbor Freight at 30 psi. I found the water quantity recommended to make up the Deft too high, it made the paint too liable to run. I also found that the Deft likes to set up a bit before adding the water, so hold off on the water for a few minutes while stirring until the viscosity comes up and a good colloidal suspension is seen. OK, I am not the worlds champion spray artist. The hardest part was holding the parts while spraying, I found that a surgeons clamp pliers worked well ($2.00 at the Salinas air show), but I still found unsprayed areas after the paint cured. I found that a foam block brush was best for touch up, if you use a bristle brush it leaves lines and the hair gums together. Forget latex gloves, they fall apart in the Deft. Use the strong yellow ones, from Lucky’s at $1.99 a pair.
On the TSP box it says Do Not Use On Aluminum. This is because this material hydrolyses in water to give a fairly strong caustic solution, pH of around 9.5 which if left on for hours might etch the surface (sodium aluminate is formed). You want something to bite into the aluminum just a little. A few minutes while you wash it does not harm at all. (This should bring the skeptics out in force…) I can also run TSP down the drain without killing all the bugs in the sewerage farm and the fish in the bay, it is safe to dispose of it in this way.
Some people will comment that this is as much trouble as Alodine, but I found TSP at Home Depot and could not find Alodine anywhere. My metal finishing experience gave me the background to put together a process that worked. I can’t get the Deft off once I put it on. Acetone won’t touch it and you have to grind or sand it to remove it.
–Chris Lowery
