Alodine (chromic acid, a carcinogen) is the 'bad sister' conversion coating. It is the wash treatment of choice. Some details in the posts above here.
All the reading I've done shows everybody uses it in conjunction with the phosphoric acid etch.
We may be having a problem here with the word PRIMER.
The two WASH & RINSE treatments are not primers in the sense of a coating - altho the chromate wash leaves a film behind. That film is supposedly THE corrosion protector. But its main claim is that it bonds to aluminum and paints bond to it. And bonding is corrosion protection.
It so far looks like epoxy paint primers with chromate used over the corrosion treatment are extra insurance in the eyes of the guy who's using it. There might be no need for them.
Can a chromated epoxy primer be used as a corrosion blocker on acid washed (Alumiprep 33) aluminum? Without using the 'traditional' conversion (Alodine) coat? www.aircraftfinishing.com Stewart makes only waterborne primers and paint. They have a one part non-catalysed non chromated epoxy primer that one guy anyway on vansairforce.net forums says can do just that. Go on bare scuffed aluminum............ayeduno.
If we sand with nothing coarser than 80grit on the mast, and nothing coarser than 180grit for any subsequent sanding before the first chromate conversion coat, it has been said we are more likely to make a technical transition from prep to coating stage. Coarser grit sanding "imbeds impurities" that will come back later to screw up paint integrity. Sanding a more uniform surface without deep scratches allows the film more uniform coating.
The insurance of including chromated epoxy primers is for some painters unavoidable because of aggresive or not sure sanding prep. Or on the mast I'm in charge of, a surface of 1000s of unknown tips and crannies.
A 45 year old mast has porosity issues that thin guage furniture or hotrod aluminum sheet (that is going to be painted) doesn't have.
litlgull's mast has countless visible scars with corrosion in them. Time,neglect, and sodium chloride have left an aluminumscape of unseen pin holes and mini fissures everywhere on its surface. Can't sand away old age.
Ben, I cannot find provenace for not including the Alodine film treatment. I don't want to use it.
The first epoxy primer always seems to be a corrosion blocker.
To be a useful as a corrosion proof coating, the epoxy primer has to be water thin so that it migrates/penetrates into the smallest imperfections on the mast surface.
SherwinWilliams supplies paint to the USNavy. They also have a specific epoxy chromated primer that is meant to go over a chromated conversion film. BUT
On the SW website we can find out what was used to renovate the USS Yorktown, now a "coastal Landmark". SW's schedule for renovating the coatings on the WWII aircraft carrier consisted removing most of the old and then a prime coat of organic zinc at 3.5 to 5 mils. An intermediate coat of Macropoxy 646 at 5 to 10 mils. A topcfoat of High Solids Polyurethane at 3 to 4 mils. They used "automotive-type body filler" (bondo) and caulk where ever there were rust streaks! Intended life of 'system' is 20 to 25 years. Painting a gigantic tourist/historical attraction isn't like mast preservation for sure. But no conversion coatings were used!!
The normal "coatings specs for an aircraft carrier really is as thick as a phone book."
The system was designed to coat rusty steel, galvanized iron and aluminum.
There is available from AirCraftSpruce a plain zinc primer. Don't know about "organic."
Glisando Triton 381. TimLackey used Alumiprep 33 and Alodine 1201.
He left the mast's top and bottom cast aluminum fittings in place.
And also did not remove the sail track.
He went Awlgrip and used the 30-Y-94 "yellow anti-corrosive primer" on top of the conversion film. It is a two-part strontium chromated epoxy in a soup of solvents. Awlgrip LPU requires an epoxy base.
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Simple Green scrubbing of litlgull's mast revealed
crevis corrosion in every (104) mast-track screw holes. Seriously, almost every hole has starlike crevises emanating from the hole. Every screw that came out did so with a little bit of white powder.
In the dozen or so holes below the track in the flat where a short piece of aluminum track was attached with fine thread s.s. screws there was nearly no corrosion or white. DFO's did some mangling here that caused corrosion.
My advice is to bite the bullet and remove EVERYTHING from your mast when renovating. Even if you are not going to paint it!
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I thought SimpleGreen was an environmental product.
Seems many people do. On my now almost empty qt spray bottle it says, "non-toxic and biodegradable."
When trying to find the msds the maker won't reveal ingredients in the formula 'to protect it from piracy'.
The Environmental Working Group, a consumer watchdog takes exception to that. It evidently didn't take industrial espionage for EWG to get an analysis of the cleaner that found 2-butoxyethenol, a carcinogen,
and 66 OTHER CHEMICALS IN SIMPLEGREEN including formaldehyde. Listed on their website.
What's in your detergent?