Date: Mon, 3 Mar 1997 11:26:32 -0600 (CST) From: Greg Smith Subject: COZY: Metal Prep Hi all, I've been wondering how to prepare aluminum parts (that have been alodined) for bonding, such as elevator tubes, canard lift tabs, etc. After the alodine, are these parts sanded (220gt) or just installed and glassed over as they are? Greg Smith gssmith@connecti.com From: Marc J. Zeitlin Subject: COZY: Metal Prep (fwd) Date: Tue, 4 Mar 97 9:27:56 EST Greg Smith wrote: >I've been wondering how to prepare aluminum parts (that have been alodined) >for bonding, such as elevator tubes, canard lift tabs, etc. After the >alodine, are these parts sanded (220gt) or just installed and glassed over >as they are? I've been holdiing off on throwing in my $0.02 in hopes that someone who knew what they were talking about would do so :-), but no-one has in a couple of days, so here goes. AFAIK (As Far As I Know), the plans do not mention any treatment of aluminum parts that eventually get floxed or otherwise bonded into the structure. They DO explicitly mention sanding or roughing up the surface of these parts prior to bonding. My personal belief is that it would be better to bond directly to the aluminum surface rather than to some paint. If you sanded the paint, you'd just take it off anyway and a glue joint to the paint is no better than the paint adhesion to the metal. There was a discussion a while back (I'm sure it's in the archives somewhere) about some canard lift tabs that had been corroded and had to be replaced, but Fred Mahan pointed out that these particular ones had been left out in the salt spray in Florida for a couple of years, not attached to an airplane. If that's what it takes to get corrosion, I'm not particularly worried. Totally exposed external metal (rudder belhorns, etc.) would be another story, however. -- Marc J. Zeitlin Email: marcz@an.hp.com From: Epplin_John_A@hpmail1.90.deere.com Date: Tue, 4 Mar 97 09:11:49 -0600 Subject: COZY: Metal Prep (fwd) > Greg Smith wrote: > > >I've been wondering how to prepare aluminum parts (that have been alodined) > >for bonding, such as elevator tubes, canard lift tabs, etc. After the > >alodine, are these parts sanded (220gt) or just installed and glassed over > >as they are? > > I've been holdiing off on throwing in my $0.02 in hopes that someone who > knew what they were talking about would do so :-), but no-one has in a > couple of days, so here goes. AFAIK (As Far As I Know), the plans do not > mention any treatment of aluminum parts that eventually get floxed or > otherwise bonded into the structure. They DO explicitly mention sanding > or roughing up the surface of these parts prior to bonding. My personal > belief is that it would be better to bond directly to the aluminum > surface rather than to some paint. If you sanded the paint, you'd just > take it off anyway and a glue joint to the paint is no better than the > paint adhesion to the metal. > > There was a discussion a while back (I'm sure it's in the archives > somewhere) about some canard lift tabs that had been corroded and had to > be replaced, but Fred Mahan pointed out that these particular ones had > been left out in the salt spray in Florida for a couple of years, not > attached to an airplane. If that's what it takes to get corrosion, I'm > not particularly worried. > > Totally exposed external metal (rudder belhorns, etc.) would be another > story, however. > > -- > Marc J. Zeitlin Email: marcz@an.hp.com > I will add my .02 worth, guaranteed worth at least that much. I don't remember where I ran across this but it makes some sense. Sand the AL parts wet with epoxy. I prepare the part and clean with acetone to remove any grease etc. then coat with a thin coat of wet epoxy and sand with 3M wet-or-dry 220 or 180 grit. I then wipe off as much as I can with a clean shop rag, no solvent of any kind, and install the part. This allows the epoxy to contact the aluminum before any oxygen gets to it. Sounds good anyhow. Alodine is supposed to provide a good surface for paint adhesion. I would guess that would apply to epoxy also. You could sand before applying the Alodine treatment and then wet sand as I described above at the final installation. John Epplin Mk4 #467 From: "Krasa, Paul" Subject: COZY: Metal Prep (fwd) Date: Tue, 4 Mar 1997 10:13:15 -0500 There was a discussion a while back (I'm sure it's in the archives somewhere) about some canard lift tabs that had been corroded and had to be replaced, but Fred Mahan pointed out that these particular ones had been left out in the salt spray in Florida for a couple of years, not attached to an airplane. If that's what it takes to get corrosion, I'm not particularly worried. The lift tabs were inbedded in the canard not left out exposed to salt spray, and after some thought, I disagree with Fred's analysis of the cause. If the corrosion had been caused from the canard being exposed to the elements while just sitting, the whole lift tab would have been corroded, but the part of the lift tab that was corroded was the part embedded in the flox. There was very little indication if any of corrosion on the part of the lift tab that was not embbeded in the canard. This problem is not new. There was a simular problem reported years ago with the wing attachment fittings on the Vari Ese. I believe the Vari Ese was in Ohio which is along way from the ocean. I will stick with the analysis from the corrosion expert at the Material Science Lab at Kennedy Space Center; he said that the corrosion was caused by the natural microcracking of the flox and the subsequent wicking action of moisture into the pourous material. Micro cracking is an inherent part of all composites, and is more apparent in composites made from chopped fibers. Furthermore, the canard did not set out in the elements, it was in storage in the previous owners two car garage. This is not meant in any way to slam, flame or other wise discredit Fred. I have the up most respect for him. It is just an attempt to try to set the record straight. Corrosion is a problem in all airplanes, and has a funny way of sneaking into composites. Paul Krasa Long EZ 214LP Date: Tue, 04 Mar 97 10:13:42 EST From: "KEN SARGENT" Subject: Re: COZY: Metal Prep (fwd) I have had the opportunity to research this for my work. I had asked the Naval Air Re-work facility what it does to aluminum. I've also looked over what aluminum boat builders typically do before painting their boats. When coating to aluminum, a conversion process is recommended. Aluminum will oxidize in seconds in air which hampers bonding to the surface. So... Clean with SS brush and sand Degrees with reagent grade acetone or MEK. Immediately scrub with phosphoric acid solution (Ortho in most hardware stores) and scotchbright. This will convert the aluminum surface from a loose adhering oxidation to a tightly adhering aluminum phosphate. The surface will have phosphate crystalls on it that serve as bond sites. Rinse with deionized water. Alodyne is a zince chromate acid that should improve both corrosion and bite. I don't know if this is Alodine sold in Wicks. Make sure all exposed surfaces are treated and cured properly to instructions on label. This coating is wiped on, converts the surface, and is wiped off in a few minutes. Heating the aluminum part to 150 degrees will speed up the conversion and treatment. The zinc chromate will provide a corrosion resistant layer inbetween the raw aluminum and what your sticking it to. Oven dry the aluminum. This surface is dryed and should be bonded in as soon as possible ______________________________ Reply Separator _________________________________ Subject: COZY: Metal Prep (fwd) Author: "Marc J. Zeitlin" at disney-wdw-internet Date: 3/4/97 9:27 AM Greg Smith wrote: >I've been wondering how to prepare aluminum parts (that have been alodined) >for bonding, such as elevator tubes, canard lift tabs, etc. After the >alodine, are these parts sanded (220gt) or just installed and glassed over >as they are? Mark Wrote I've been holdiing off on throwing in my $0.02 in hopes that someone who knew what they were talking about would do so :-), but no-one has in a couple of days, so here goes. AFAIK (As Far As I Know), the plans do not mention any treatment of aluminum parts that eventually get floxed or otherwise bonded into the structure. They DO explicitly mention sanding or roughing up the surface of these parts prior to bonding. My personal belief is that it would be better to bond directly to the aluminum surface rather than to some paint. If you sanded the paint, you'd just take it off anyway and a glue joint to the paint is no better than the paint adhesion to the metal. Date: Tue, 04 Mar 1997 10:25:50 -0500 From: william l kleb Organization: NASA Langley Research Center Subject: Re: COZY: Metal Prep Marc J. Zeitlin wrote: > > My personal belief is that it would be better to bond directly > to the aluminum surface rather than to some paint. the big problem with aluminum is that it starts oxidizing the second it is exposed to oxygen, so unless you do some extremely special things (like working in an oxygen-free environment), you are always bonding to the oxide layer. the trick is to get the best oxide layer possible. this is what anodizing is all about: getting a nice, stable oxide layer. unfortunately, that is as far as i've gotten in my research of this area... :( my current plan is to have my aluminum parts anodized, aka, `hard coated'(?) at my local metal finisher for ~$50 a batch (check your yellow pages). i have heard about using alumiprep and then alodine; but as of yet, i have no idea exactly what these products accomplish. -- bil Date: Tue, 04 Mar 1997 10:44:32 -0500 From: Mahan Subject: Re: COZY: Metal Prep william l kleb wrote: > > i have heard about using alumiprep and then alodine; but as > of yet, i have no idea exactly what these products accomplish. > Bill, they do the same thing that anodizing will do for you: etch the aluminum. The prep gets all of the extraneous stuff off of your aluminum, and the alodine chemically etches it. Gives it a nice gold color. After you get it to the color you want, you rinse the aluminum with water to halt the process. Anyway, the color is very thin, a transparent gold stain, really, much thinner than anodizing. You can buy the prep and alodine at your local automotive paint store by the gallon. It's easy to use. I plan on alodining all inaccessible, buried, or visible parts this time around. Fred in Florida Long-EZ N86LE Defiant project Date: Tue, 04 Mar 1997 10:54:23 -0500 From: Mahan Subject: Re: COZY: Metal Prep (fwd) Krasa, Paul wrote: > > Furthermore, the canard did not set out in the elements, it was in storage in the > previous owners two car garage. > I stick with the information from my source, that this canard sat on the screened-in back porch of a house on a salt-water canal for two years. Fred in Florida Long-EZ N86LE flying Definat under construction <331C3EFE.ABD@ab00.larc.nasa.gov> Date: Tue, 4 Mar 1997 11:13:35 -0500 From: "David R. Kuechenmeister" Subject: Re: COZY: Metal Prep I've iridited the castings for the Long EZ nose gear. I didn't plan to do any more, but the discussion here has persuaded me otherwise. Sounds like I want to sand the parts for floxing before I treat them. Then after iriditing ( alodine ), I just stick them in the flox and the parts are safe from corrosion? At 10:44 AM -0500 3/4/97, Mahan wrote: >Bill, they do the same thing that anodizing will do for you: etch the >aluminum. The prep gets all of the extraneous stuff off of your >aluminum, and the alodine chemically etches it. Gives it a nice gold >color. After you get it to the color you want, you rinse the aluminum >with water to halt the process. Anyway, the color is very thin, a >transparent gold stain, really, much thinner than anodizing. You can >buy the prep and alodine at your local automotive paint store by the >gallon. It's easy to use. I plan on alodining all inaccessible, >buried, or visible parts this time around. > >Fred in Florida >Long-EZ N86LE >Defiant project Thanks, Dave -- David R. Kuechenmeister Long-EZ #779 (770)528-7738 Atlanta, Georgia Date: Tue, 04 Mar 1997 16:21:02 +0000 From: robin du bois Subject: COZY: Re: Just a quick note, I found that safety-poxy and RAE both adhere to alodined surfaces like they grew together.. rdb Date: Tue, 4 Mar 1997 09:41:36 -0700 (MST) From: Ron Lee Subject: Re: COZY: Metal Prep At 10:44 97/3/04 -0500, you wrote: >> >Bill, they do the same thing that anodizing will do for you: etch the >aluminum. The prep gets all of the extraneous stuff off of your >aluminum, and the alodine chemically etches it. Gives it a nice gold I plan on alodining all inaccessible, >buried, or visible parts this time around. > >Fred in Florida My question to Fred (or others). Will you completely treat all metal that will be embedded in flox, such as the pieces that stick in the canard and hold the elevator torque tube (CS3)? Or will you sand the area that is to be floxed to remove the coating (alodine)? It may be that the holes in the CS3 parts, when inserted into wet flox, provide the necessary strength to retain them. The Long-EZ plans do say to sand the metal before inserting into flox. This is the inconsistency. If you sand to remove the alodine, you have no metal protection. But a recent canard pusher mentioned that these very pieces (CS3 on the canard if my memory is correct) were found to have corrosion. The builder had to remove the pieces and replace them. Ron Lee Date: Tue, 04 Mar 1997 13:06:33 -0500 From: Mahan Subject: Re: COZY: Metal Prep Ron Lee wrote: > > At 10:44 97/3/04 -0500, you wrote: > >> > >Bill, they do the same thing that anodizing will do for you: etch the > >aluminum. The prep gets all of the extraneous stuff off of your > >aluminum, and the alodine chemically etches it. Gives it a nice gold > I plan on alodining all inaccessible, > >buried, or visible parts this time around. > > > >Fred in Florida > > My question to Fred (or others). Will you completely treat all metal > that will be embedded in flox, such as the pieces that stick in the canard > and hold the elevator torque tube (CS3)? Or will you sand the area that > is to be floxed to remove the coating (alodine)? It may be that the holes > in the CS3 parts, when inserted into wet flox, provide the necessary > strength to retain them. The Long-EZ plans do say to sand the metal > before inserting into flox. > > This is the inconsistency. If you sand to remove the alodine, you have > no metal protection. But a recent canard pusher mentioned that these > very pieces (CS3 on the canard if my memory is correct) were found to have > corrosion. The builder had to remove the pieces and replace them. > > Ron Lee Here's what I'm going to do, Ron: sand the part, THEN alodine it. Alodining is an etching process which roughens the metal anyway. After alodining is complete, coat w/wet flox per plans and install. Fred in Florida Date: Tue, 4 Mar 97 14:40:52 -0500 From: kevin@ias.com (Kevin R. Walsh) As I know a LITTLE about aluminum coating, I thought I would throw in my $.02 (currency exchange rates may vary, service charges apply). We have aluminum coated with many different processes here for application in machines and also bio-tech eqpt. The following is a list of what we have had done: MIL-C 5541 E Clear or Yellow Iridite MIL-A-8625 E Type II Sulfuric Anodizing (Black and Clear are most common) MIL-A-8625 E Type III Sulfuric Anodizing (Clear) The Type III is commonly called "hardcoating" and although it is spec'ed clear, the parts come out black. We have also had parts nickle plated. We use Type II for general anodizing, when the part is not subject to wear or chemical attack. Type III is used in high wear areas and also when the parts will come in contact with bleach solution, up to 10%, submerged for extended periods. The nickle plating is used when higher bleach concentrations are used, or a silver finish is required for medical applications. I have never tried to epoxy onto anodizing, nor do I know what the process does to the overall or fatigue strength. A Type II anodizing will actually add a small layer of oxide onto the part, making it "grow" slightly. A Type III will etch the surface much more deeply before adding the oxide layer, and will tend to "shrink" the parts slightly. Iridite is such a thin layer that you will not notice any dimensional changes. Nickle plating is also a very thin layer, and no domensional changes should be apparent. This finsh also wear off very easily with excessive polishing, etc. Hope I have added to the confusion. Kevin R. Walsh Mechanical Engineer Intelligent Automation Systems 149 Sidney Street Cambridge, MA 02139 TEL 617.354.3830 FAX 617.547.9727 Date: Tue, 04 Mar 1997 15:41:38 -0800 From: berkut@loop.com Subject: COZY: Re: COZY/ Alodyne >Just a quick note, I found that safety-poxy and RAE both adhere to >alodined surfaces like they grew together.. >rdb > > All epoxy's do. They like Anodized even better - it's the only way to make _sure_ that epoxy will bond to aluminum. We sandblast and apply epoxy immediately, but even that's not at good as anodizing. -- Czech Sikhs! Richard Riley "Heavier than air flying machines are impossible." Lord Kelvin, President, Royal Society, c 1895 See the Berkut at http://www.berkut.com From: "Rob Cherney" Organization: Ellicott City, Maryland Date: Tue, 4 Mar 1997 21:25:09 -0400 Subject: Re: COZY: Metal Prep Greg Smith wrote: >I've been wondering how to prepare aluminum parts (that have been alodined) >for bonding, such as elevator tubes, canard lift tabs, etc. After the >alodine, are these parts sanded (220gt) or just installed and glassed over >as they are? Here's what I've been doing: First, I sand blast the part. Then, I wash with "Alumiprep" followed by an alodine treatment. After the alodine, I dry the part and glue it to whatever with Hysol EA-9330. My experience has been that this epoxy bonds well with aluminium if it has been properly cleaned and treated. The Hysol needs to be mixed in a big enough quantity to get an accurate mix ratio, otherwise it loses much of its potential strength. In some instances, I need to precoat (with a disposable brush) the part with Hysol since I will be applying a subsequent laminate on top of the piece. Once the precoated part has cured, I lightly sand it with 80 grit. Secondary bonds with Epolite have been good using this technique. Rob- +--------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@clark.net | +--------------------------------------------------------+ Date: Tue, 4 Mar 1997 23:32:34 -0500 (EST) From: StetsonE@aol.com Subject: COZY: Re: COZY/ Alodyne The Long-EZ plans say nothing about protecting metal parts from corrosion. However, the CP newsletters do cover the subject, as given below. Sorry for the length, but there seems to be considerable interest. Note when reading the articles that anodizing and alodining are not the same process. FWIW, I didn't treat any of my aluminum parts. My project has lived near the coast for all of its 11 year life and I haven't noticed any evidence of aluminum corrosion (yet). I tried alodining and couldn't get consistent results - the coating seemed somewhat mottled. For bonding purposes though, that probably wouldn't have mattered. **From CP38-4** Aluminum Corrosion Out here in the desert corrosion is not a problem. Some builders however, do live in highly corrosive environments. Rodie Rodewald is one. On the north shore of Oahu Island in Hawaii, where the biggest surf in the world breaks is where Rodie keeps his VariEze and Long-EZ. The air is literally heavy with salt spray all the time and Rodie has found exposed aluminum parts, not anodized, will corrode. He strongly recommends anodizing and insists that it is easy and fun to do. All you need: 1 gallon plastic jug cut off to make a bucket. 1 gallon of battery acid (H2SO4) at a specific gravity of 1.10. A lead plate a little larger than the parts to be anodized. 12 volt battery charger (6 amps is best). Pure, soft aluminum wire. Trisodium phosphate (TSP) available at hardware stores, diluted .80 ounces per gallon of water. Cleanliness is very important to success. He used wooden tongs and chop sticks to handle all parts after cleaning and proceeded in the following way: Degrease all parts to be anodized. Heat TSP to boiling, cool to just under boiling, immerse parts 3 minutes. Water rinse avoiding touching the parts. To anodize: Positive lead to parts. Negative lead to lead plate. Use the aluminum wire. A good contact is the secret to success. Gas bubbles evolving from the lead plate proves that anodizing is occurring. Leave parts in the anodize process 25 to 30 minutes. Water rinse. Boil parts for 10 minutes in tap water to seal the anodizing. The only caution note is to be careful with the acid. It is not a strong acid, but acid is acid and can burn, therefore use personal protection of skin and clothing and in event of an acid spill, wash thoroughly in baking soda and water. **From CP53-7 ** CAUTION: CORROSION IN VARIEZE WING ATTACH FITTINGS A VariEze which had spent most of its life outdoors in the eastern US, but significantly, not on the coast, was found to have severe intergranular corrosion in the top plates of the wing attach fittings as well as in the two aluminum tubes between the top and bottom plates. Very little evidence of this was visible upon casual inspection. However, when the UND wrap on each end of the centersection spar was lifted, the corrosion was rampant and this EZ builder said he would not have flown this airplane knowing how bad the corrosion was. All VariEze owners should make a very careful inspection of the aluminum wing attach fittings, especially under the glass that laps onto the aluminum plates, particularly if there is evidence that the glass has peeled or delaminated from the wing attach plates, both on the wings and the centersection spar. For new construction, all aluminum parts, including wing attach fitting, should be cleaned in Alumiprep33 or metal prep #79 and then soaked in Alodine 1201 which is a visible (golden brown) moisture barrier, greatly increasing resistance to corrosion. This also acts as an excellent surface to bond epoxy or paint. Do not anodize wing attach fittings since this finish, if not done exactly right, can cause embrittlement in the highly stressed wing attach parts. Alodine is a common aluminum preparation and can be obtained from RAF-approved suppliers such as Aircraft Spruce or Wicks Aircraft. ** This next article is quite long. I deals mainly with the task of removing corroded wing attach fittings in VariEzes. I've posted only the portions that are applicable to Cozy builders.** **From CP55-5** VARIEZE MAIN WING ATTACH - CORROSION New construction VariEzes, or anyone replacing wing attach fittings with new ones, should clean all aluminum parts with Alumiprep 33 or Metal Prep #79 then alodine them with Alodine 1201 which puts a tough, corrosion-resistant, visible, golden finish on. We are reluctant to try alodining parts in place due to the acid etch (Alumiprep 33) possibly getting under the glass onto the aluminum. Sea planes are especially prone and require constant inspection and maintenance aimed at preventing just this problem. The salt in the air plus water from rain or condensation, plus heat and aluminum and, presto!, you have a battery! Galvanic reaction and you have corrosion. Keep the aluminum parts clean, grease them often, and you will have no problems. People who live far from the ocean may not see this problem but they must check for it just the same. This problem is confined to the VariEze. The Long-EZ wing attachment is completely different and this same problem should not occur. Of course, all metal parts must be protected from corrosion - aluminum with alodine or zinc chromate, steel with zinc chromate (after cleaning in metal Prep). Wing attach bolts and parts should be generously covered with a good grease in VariEze and Long-EZs. Replace any rusty bolts and nuts. Hope this sheds some light on the subject. Stet Elliott stetsone@aol.com Perpetual Long-EZ builder Date: Thu, 6 Mar 1997 23:43:34 -0500 (EST) From: SMilesCozy@aol.com Subject: Re: COZY: Metal Prep / Corrosion Prevention In a message dated 97-03-03 12:36:03 EST, you write: > I've been wondering how to prepare aluminum parts < On Chris van Hoof's recomendation I purchased Andrew Marshall's "Composite Basics." I highly recomend it, It's in an easy to understand format. In chapter 11 he writes, "With the passage of time, bonded aluminum joints made to perfectly clean but untreated aluminum surfaces experience a reduction in strength that is insidious. The adhesive shows an attractive and high strength level immediately after cure, (wether room temperature or elevated temperature system), but then begins to show progressively lower strengths after longer exposure to normal storage conditions. There is no clear relationship between the amount of time that has passed and the amount of reduction in the strength of the joint. It has been determined, however, that either the presence of high humidity or a high stress level will drastically accelerate the deterioration; if both are present, the loss of strength occurs even more rapidly." Pretty scary! In appendix 4 he quotes from an article titled "No More Rivets" written by Mr. Otis Holt. "The technique prescribed for bonding my wings consists of thouough scuffing the bond area using an abrasive disk, meticulously wiping the surface with Methyl Ethyl Ketone, and bonding directly to the bare aluminum using a room temperature curing two-part epoxy. Let's call this the scuff / wipe method. Marshall assured me that, while such bonds may initially appear quite strong, they are not reliable. In fact, he claimed that, given sufficient time and environmental exposure, (particularly any form of moisture), delamination is inevitable." "But Marshall, and others, have verified thtat even if the oxide layer in a bare metal bond were non-existant or of acceptable quality initially, condensation and humidity exposure would result in oxide formation and / or degradation beginning at the unprotected edges of the joint and migrating across the bond interface, eventually resulting in complete delamination." Without quoting the rest of the article, he comes to the conclusion that the best way to assure a long term bond to aluminum is to use an FPL etch, with a Phosphoric Acid Anodize, or a Chromic Acid Anodize, with a special corrosion-inhibiting adhesive primer applied before bonding. Needless to say, this is beyond the scope of most junior chemistry sets. :^) He found a local Aerospace contractor, in his native So. California, to treat his two skins, two spars, and about 70 stamped ribs and miscellaneous parts to Boeing specification BAC5555 for $500.00 in 1984 dollars. Since I live in the St. Louis area, with McBoeing Douglas in town, I think I'll see if I can find someone to prep my aluminum parts to this specification or one like it. Steve (I'm affraid of corrosion) Miles Cozy MkIV 272 Date: Thu, 6 Mar 1997 21:59:54 -0700 (MST) From: Ron Lee Subject: Re: COZY: Metal Prep / Corrosion Prevention I was just scanning my Canard Pushers for another topic and believe that I saw a notice on elevator tube corrosion. It recommended for new construction that the tube be alodined. Another poster earlier stated that bonding to alodined aluminum is NOT a problem. Ron Lee >Without quoting the rest of the article, he comes to the conclusion that the >best way to assure a long term bond to aluminum is to use an FPL etch, with >a Phosphoric Acid Anodize, or a Chromic Acid Anodize, with a special >corrosion-inhibiting adhesive primer applied before bonding. Needless to >say, >this is beyond the scope of most junior chemistry sets. :^) > >He found a local Aerospace contractor, in his native So. California, to treat >his two >skins, two spars, and about 70 stamped ribs and miscellaneous parts to >Boeing specification BAC5555 for $500.00 in 1984 dollars. Since I live in >the >St. Louis area, with McBoeing Douglas in town, I think I'll see if I can find > >someone to prep my aluminum parts to this specification or one like it. > >Steve (I'm affraid of corrosion) Miles >Cozy MkIV 272 > > Date: Fri, 7 Mar 1997 13:39:14 -0500 From: Rick Roberts <102503.1561@compuserve.com> Subject: Re: COZY: Metal Prep / Corrosion Prevention I used to use Phosphoric Acid Anodize at GD in San Diego, it has been recognized by many sources as the number 1 surface preparation for aluminum for bonding. If I remember right according to BAC 5555, you have seven day to get the adhesive on the surface. After that it starts to detoriate. The surface is very fragile don't scuff it or rub it prior to bonding. (especially don't solvent wipe it). If you can get a large oven or get someone at an aerospace company to help you get them to put on what used to be BR127 primer from American Cyanamid. Then the shelf life is nearly infinite, and easily handled. The surface thickness of the anodic coating and the primer is about 0.001" thick so don't get brutal with sandpaper or anything. Rick Roberts From: Marc J. Zeitlin Subject: Re: COZY: Metal Prep / Corrosion Prevention (fwd) Date: Fri, 7 Mar 97 14:23:57 EST People; I don't mean to diminish the importance of surface preparation of aluminum prior to bonding (but I'll do just that :-) ). Clearly, there are many ways to maximize the corrosion resistance of aluminum and the bond strength of aluminum to epoxy. Any of these is probably better than doing nothing (or just 220 grit sanding and cleaning of the aluminum). However, I've got to say that I find it hard to believe that after 20 years of thousands of canard composite aircraft being built and flown in any and all environments with NO special surface preparation called out in the plans (VE, LE, Cozy), that all this surface prep. is _necessary_. That's not to say that it's not a good idea, or not good insurance, but these planes would be falling out of the sky left and right due to corrosion if this was a real problem. Maybe I'm a pollyana here, and I'm not really looking to stir up a hornet's nest of debate about this, but theoretical problems don't always turn into real ones. My $0.02. -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Fri, 7 Mar 1997 16:23:03 -0500 (EST) From: DFinn7971@aol.com Subject: Re: COZY: Metal Prep / Corrosion Prevention (fwd) In a message dated 97-03-07 14:56:13 EST, marcz@hpwarhw.an.hp.com (Marc J. Zeitlin) writes: << However, I've got to say that I find it hard to believe that after 20 years of thousands of canard composite aircraft being built and flown in any and all environments with NO special surface preparation called out in the plans (VE, LE, Cozy), that all this surface prep. is _necessary_. >> I guess I have to agree with Marc that the extra effort involved with surface preparation is probably not necessary. I'm sure that corrosion could eventually be a problem, even in the midwestern states (far from the salt spray), after some unspecified number of years. I can't help but wonder if the epoxy would deteriorate faster then the corrosion would appear. Bottom line being that eventually any plane (aluminum, wood or composite) will deteriorate. Good care can add years to the lifetime. I suspect that after 20 years we will all be looking at replacing things (ranging from cables and bearings all the way to airframe components). Despite the feelings I have expressed, I intend to go over to the auto parts store and buy the alodine treatment. I'm doing this for the same reason that I'm polishing the exposed aluminum parts and double and triple checking each measurement. I want this plane to represent my best efforts at quality. Dick Finn Date: Tue, 04 Nov 1997 14:26:22 -0800 From: Stetson Elliott Subject: Re: COZY: anodining aluminum Paul Burkhardt wrote: > I recall someone posting a how to anodine (or is it anodize ?) > aluminium > using battery acid and a power supply. Can you send me the information > > again I cant seem to find it in my long list of cozy e-mail. > Paul Burkhardt I think that was me. Here's the relevant article from Canard Pusher Newsletter 38: Aluminum Corrosion Out here in the desert corrosion is not a problem. Some builders however, do live in highly corrosive environments. Rodie Rodewald is one. On the north shore of Oahu Island in Hawaii, where the biggest surf in the world breaks is where Rodie keeps his VariEze and Long-EZ. The air is literally heavy with salt spray all the time and Rodie has found exposed aluminum parts, not anodized, will corrode. He strongly recommends anodizing and insists that it is easy and fun to do. All you need: 1 gallon plastic jug cut off to make a bucket. 1 gallon of battery acid (H2SO4) at a specific gravity of 1.10. A lead plate a little larger than the parts to be anodized. 12 volt battery charger (6 amps is best). Pure, soft aluminum wire. Trisodium phosphate (TSP) available at hardware stores, diluted .80 ounces per gallon of water. Cleanliness is very important to success. He used wooden tongs and chop sticks to handle all parts after cleaning and proceeded in the following way: Degrease all parts to be anodized. Heat TSP to boiling, cool to just under boiling, immerse parts 3 minutes. Water rinse avoiding touching the parts. To anodize: Positive lead to parts. Negative lead to lead plate. Use the aluminum wire. A good contact is the secret to success. Gas bubbles evolving from the lead plate proves that anodizing is occurring. Leave parts in the anodize process 25 to 30 minutes. Water rinse. Boil parts for 10 minutes in tap water to seal the anodizing. The only caution note is to be careful with the acid. It is not a strong acid, but acid is acid and can burn, therefore use personal protection of skin and clothing and in event of an acid spill, wash thoroughly in baking soda and water. -- Stet Elliott flyez@earthlink.net Long-EZ N321EF Date: Fri, 21 Nov 1997 23:05:48 -0500 (EST) From: Nigel Field Subject: Re: COZY: Brock / metal parts-Reply At 05:53 PM 11/21/97 -0600, cdenk@ix.netcom.com wrote: >There has been considerable traffic recently on making parts nomally >furnished by Brock. > >With the local EAA newsletter the following came, its from NASA documents. > >"Hydrogen Embrittlement occurs whenever thre is free hydrogen in close >association with the metal. Since most plating processes are the >electrolytic bath type, free hydrogen is present." Summing the related >problems: "Hydrogen reacts with carbon in steel ... reduce the overall >strength", Internal hydrogen embrittlement ... delayed failure after proof >testing", "Hydrogen environment embrittlement" ... Not a factor unless >fastener under stress in a pressure vessel. Very true and good advise, but there is an obvious solution. Don't plate your parts. All my parts are homemade on both my Vari-eze and Cozy. None are plated because it is not necessary. None have corroded either. Most are protected with epoxy primer and paint. Some such as the wing attach taper pins on my VE have been tinned with common solder using flux a torch and steel brush then wiped with a rag while still molten. Its as good as cadmium to prevent corrosion (rust) on steel parts. Nigel Field Date: Sat, 22 Nov 1997 11:07:49 -0500 From: bil kleb Organization: NASA Langley Research Center Subject: Re: COZY: Brock / metal parts-Reply cdenk@ix.netcom.com wrote: > > many plating houses may not be able to do properly. many plating houses already are certified to produce parts according to mil-specs. just be sure and ask them what sort of people they've done work for. if they respond saying army, navy, etc. you know they know how to deal with government inspectors and paperwork to do the plating properly. -- bil From: AlWick@aol.com Date: Sun, 23 Nov 1997 01:11:16 -0500 (EST) Subject: Re: COZY: Brock / metal parts-Reply In a message dated 97-11-22 01:22:55 EST, cdenk@ix.netcom.com writes: << DO not take the above as instructions, but as an indicator of complicated procedures that must be followed, and many plating houses may not be able to do properly. >> Hydrogen embrittlement was not a factor on any parts I made. I did not need to plate any of them. I used iron phos, or both iron phos and powder coat. Hyd. Emb. applies only to high carbon materials and only certain plating processes. Zinc plated grade 8 bolts are a good example of a genuine risk. Nothing magical about the baking process in my opinion. I'm sure it doesn't need be said, but anyone concerned about making Brock parts should probably buy them. Same with spars, wings, ..... To each his own. FWIW. -al