a little corrosion goes a long way
Carl,
Way back when:
I got a brand new set of airfoil spreaders.
They want a new way of attachment to the mast, counter-intuitive to our bolt, socket and pole method.
So I got them out again and discovered the anodising was chipping off on the LEADING EDGE of both foils. They've been going to weather in the carton they've been stored in, sailing around in a wet mineral dream for years & years.
Anodizing is an electro dip method for increasing oxidation on aliminum. It's thicker, but in microns.
Don't know how the prep was done, but somebody screwed up. Greasey fingers.
These pieces of aluminum will now start oxidizing on the leading edges and the remaining anodizing will become a cosmetic problem. Anodizing makes aluminum look sexy, but the metal if left alone will on its own put on a tough protective dull grey coat. After 45 years it needs more help than self oxidation gave it. Where holes pierced it, stuff hung on it, wires slapped against it, salt chewed on it, needs some kind of help.
litlgull's mast has too many imperfections to be sanded to perfection and just left alone to develop the protective coating on its own. There is no way of stopping oxidation from forming. Even on a shabby mast.
In fact aluminum is so eager to get an oxide coating (and then actually stop oxidizing after it gets that perfect thin coat)
that all this BS in the post above about outrageously priced chemicals and hours and weeks of work is dedicated to interrupt that natural process for a cosmetic payback.
If it gets dinged, only the bare, raw oxide layer of an unpainted mast can heal itself - if it has oxygen/air. But if the cosmetic spar, the muti-layered acid etcherrupticus, gets a ding...all hell breaks loose and the mast immediately gets oxide cancer. No matter what has gone before.... whatever expense it took to stop the oxidation process...
those careful layers of corrosion inhibitors, converters, primers and paint.... when a hole gets chipped in there by a shackle or block... the fancy paint job creates a perfect home for aggresive CREVIS CORROSION.:eek:
Doom bubbles on yer dream stick!
Which the plain old unpainted mast doesn't get,
except where holes are drilled, stuff attached. Sailtrack, sockets, cleats, winches.
That's why we hear all those guys yelling, Don't paint the damn mast!
Aircraft Spruce Covering Materials catalog gets failing grade from Ebb
Carl, et al, anyone having to paint aluminum. Many times ended up on DIY airplane sites.
Many times couldn't understand a word. Yes, we do have aluminum in common. Also have different problems.
May be wrong, most small plane aluminum structural parts are fabricated and finished off with anodizing before assembly.
Aircraft Spruce "Everything For Planes & Pilots" is a source for coatings and attracts guys like me who are looking for authentic products but feel pretty much like a kid outside the candystore with his nose pressed against the window. Here's the problem.
In the online Covering Materials section I concentrate on prime coatings avaiable after the Alumiprep 33 cleaner and chromate coat Alodine. That IS the coversion coat, right? OK, What's next?
The primer cycle:
AircraftSpruce pushes this brand as numero uno: PTI Speciality Paints Epoxy Primer
(accompaning photo shows aerosol cans - but none available - aerosol theorectically would make fogging thin even coats possible. Almost all aircraft coatings are sprayed on. I'm a roll and tip kind of kid because I don't have the sprayer, don't have the air suit, don't have the facilties or the facility for spraying. Most of us are in that boat, right?)
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This Epoxy Primer is a 2-part, 1 to 1, no thinner necessary (only prices for thinner shown). It has strontium (chromate?) in it - not listed on product page. Do I need another dose of chromate? There may be a roller version but that's not important to 'Spruce. Product description does NOT say the primer can be used after a conversion coat.
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PTI Acid Etch 'AirDryWash' primer. 3-part, 4 to 1 plus reducer. Polyvinyl butyral (auto safety glass), contains zinc chromate and phosphoric acid. May blush. If you put it on too thick, any next coat won't stick. Spray or dip. Prices for reducer only. Their version of Alodine.
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Zinc Oxide primer. "Chromate free, environment friendly". AEROSOL available. $9.95, coverage?
Epoxy? Petroleum solvents, waterborne?
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Zinc Chromate primer. AEROSOL available. [Can't be environment friendly.]
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PTI Waterborne Epoxy primer. 2-part, 4 to 1. Reduces with water Thincoat spray. Prices for 1 pint catalyst and 1 gal kit.
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Epibond Epoxy Primer Kits. 3-part. Single can shown in pic. Qt kit $79.50. No info.
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Stewart Systems Ekoprime Primer/Sealer. Single part, waterborne. No chromates, no catalyst, low VOC, no HazMat shipping fee (assume). Spray, but foam roller OK. Actually says it goes on after the conversion coating. $34.85 QT. Eko-material not stated.
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Stits Epoxy Primer Kits. 3 part, 2 to 1 plus reducer. Fast dry, cures down to 35F. Separate price for each part.
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PreKote Surface Pretreatment. [So what is this? A wash? A conversion treatment? An epoxy substitute? Is it waterborne? Is it 2-part? When do we use it?]
"Non hazadous, non flamable, odorless, provides corrosion protection, biodegradable, non-toxic, chrome free, enhances paint adhesion." So we slosh it on over the alodine chromate because we suddenly got eco-friendly? Seems to be reasonably priced.
There's no article covering this, no pros and cons, no advice or recommendations. Nobody talking about how this intricate system gets put together, what sticks best to what, using any of these products. Solvents in a new coat might wrinkle the previous coat. Temps,Timing, Humidity facts.
Waterborne coating can provide a solvent barrier - a solvent coating may become a tie-coat because of its solvents. Coatings with solvents require a careful cure time so no solvent outgasses into a later coating.
Private sites, blogs? .... man, I don't have the time anymore.
Snooty know-it-alls!:rolleyes::rolleyes:
So this shows, doesn't it, the quandry a nose-to-the-glass customer faces.
Who knows how to put the quarts in order?
Who's used the aerosols or the Prekote on an old mast?
Where does the third cycle actually begin? That's the last set with an epoxy sanding primer and final paint coats?
Are we here yet?