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Corrosion Prevention - 4130 Steel and Aluminum. What to use

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lcfitt(at)sbcglobal.net
Guest

Posted: Sun Apr 26, 2009 9:51 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

Mike,



I think in addition to the Alumiprep which is basically a cleaner and 

etchant, I would follow that with Alodyne which as a conversion coating with 

corrosion resistance and it enhances paint adhesion.  Alodyne is used alone 

in the interiors of aluminum aircraft as a corrosion coating.



You will need an epoxy coating where the adhesives will contact any 

structural member.  In the old days, it was a zinc chromate epoxy primer. 

This was reformulated, because of  the suspicion by the EPA that we were 

actually drinking this stuff, and now the zink chromate is available in 

aerosol spray cans - which tells us right away that it is not an epoxy 

coating - and the "green" epoxy primers claiming corrosion resistant 

properties without telling us what they contain, except maybe on the can.



I think if I were buying today, I would go with the Polyfiber product to 

keep everything consistant.  It comes in green or white.  Randolph also has 

a green or white primer as well.



A real good alternative down there would be to go to your local automotive 

paint store and see what they recommend.  They are very familiar with your 

environment and what it takes to keep things from turning orange.



Lowell Fitt

Cameron Park, CA

Model IV-1200 R-912 UL

Still building and modifying

---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Apr 26, 2009 9:51 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

Two part epoxy zinc chromate should be used.  You are almost as close to

salt water as I am, so yes slosh the inside of the spars too and hang them

vertically to drip dry.   Well at least close to vertically...  At least let

the excess drain out.



If you already have your frame then it's too late to get it powder coated

unless someone in the area does it.   I would at least give it a good coat

of two part Zinc-Chromate primer.   Painting  would be optional depending on

how strict you want to be on weight.  In this game less is much better.  



One thing I would do which is often forgotten is to inhibit the interior of

the frame.  This is done by drilling a small hole in the frame  inside where

it won't be in the way of covering or glass installation.  Using a big

syringe put about a can of double boiled linseed oil in the frame through

the hole.  Put a screw in the hole to seal it and then the fun part.  You

will want to rotate the frame and hang in every conceivable attitude for a

few hours each attitude before moving it to the next attitude.  This can

take several days.  Then turn your filling hole to the lowest point and

drain out the linseed oil.  Once you figure you have all the linseed oil out

(it will stop dripping) you can get the last couple of CCs with the syringe.

Then re install the sealing screw preferably with a bit of epoxy on it to

give it a good seal..  The top corner of the cabin seems to be a good spot

or the back of the vertical stab near the bottom to drill the hole.



One hole around 1/16 in should suffice nothing over 1/8 in..  The linseed

oil acts like a penetrant inside the frame and covers everything then it

semi hardens to a gummy sticky coating that protects from internal moisture.

You can also do the same thing with the rudder and elevators.



If you get any quantity of linseed oil on a rag  or paper make sure to

dispose of it in a fire proof container immediately.  The stuff likes to

spontaneously combust producing a thick, cut it with a knife, white smoke.

Don't ask how I know. Remember the more you put in the frame the longer it

will take to drain out.  Use no more than a couple of cups of oil you will

be surprised at how much you get back.



Inhibiting a frame almost requires the frame be in a hangar or warehouse for

that part of the build.  If you decide to powder coat it's better to inhibit

first.  Check with john and see if his frames are inhibited at the factory.

It's a one shot deal done once and never again.



The idea of the two part zinc chromate is when you go to cover, the

chemicals in the attach glue and the poly brush will dissolve a regular

spirit chromate and the attach glue may not adhere the cloth to the frame

the way you would want .

--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

larry huntley

Joined: 19 Jul 2008
Posts: 149

Posted: Sun Apr 26, 2009 10:23 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

Mike,

  Any thoughts of using a two part Urethane paint over the primer? Primers 

are just that, and should be covered with something that is not porous. It 

is often thought that because a primer is an epoxy ,it is therefore a good 

seal. Those who know much more than I tell me this is not true.

  Stewart Systems makes a good one part primer/sealer which they say will 

seal well under normal conditions,but even they say to put their 2 pt 

urethane over it if it is ,for example, a seaplane.I did that with a 

Vagabond that I am restoring even though I expect it to be hangared most of 

the time. Will try to send a pc of that in another post.         Larry 

Huntley,4-1200 Soob



---

_________________
Larry Huntley,Dundee,NY
Kitfox 4-1200 N234EE
EA81,AMAX Redrive Warp 3 blade

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Apr 26, 2009 10:44 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

Old days???  Gee I didn't think I was that old.  



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

lcfitt(at)sbcglobal.net
Guest

Posted: Sun Apr 26, 2009 4:05 pm Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

Dave,



Nope, not that old.  My first kit came with a quart of Stits "Epoxy Chromate 

Primer", that was 1993.  Today, Polyfiber lists it as Epoxy Primer and no 

mention of chromate.  They do say corrosion resistant, but somehow I think 

that might be just like the labeling on toothpaste.  Check the active 

ingredient of all toothpasts and they will list some form of fluoride. 

Check the label and they will be for cavity prevention, tooth whitening, 

ultra tooth whitening, gum disease prevention, you name it.  Sort of one 

size fits all - this from an "old" dentist.



As mentioned, zinc chromate is still available, but not as an epoxy primer - 

at least I can't find any.



Check the links below.



http://www.finishing.com/0600-0799/702.shtml



http://www.aircraftspruce.com/catalog/cspages/ptizincchromateprimer.php



Lowell

---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Apr 26, 2009 6:08 pm Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

I think you're right there Lowell.  I just checked on Rand-O-Plate which I

knew was dark green.  It is recommended for priming steel and a white is

recommended for aluminium.  I tried to find MSDS sheets on the Rand-O-Plate

with no results but I think I'd be very surprised if there was any zinc or

chromate in it.  



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sun Apr 26, 2009 6:44 pm Post subject: Re: Corrosion Prevention - 4130 Steel and Aluminum. What to

Noel,



Right now my Kit is sitting in the garage within 50 feet of salt water, to get it any closer I would have to put it on floats   I really like the idea of treating the inside of the 4130 steel tubing, I bought a can of Tube Seal, but have been wondering about putting it in.  Are there holes in all the cross members, and welded parts of that frame, or do I not need to worry about tubes that are completely sealed by welds at both ends ?   There are so many different tubes, I was wondering if I would have to drill a small hole in every tube ???   The time to do this is definitely before getting to far, later on it wont be an option.



The tubing is powder coated, but there are always scratches, and 4130 parts that need to be coated, and my friend even had places where the metal was not prepped well and the powder coating was coming off.  So I am anticipating having to re-prime some areas myself.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Apr 27, 2009 8:48 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

There are very few if any places where the tube is closed off inside a weld.

I was told that this is because it would cause twisting of the joint.  So

basically you only need one hole.  The turning of the plane with the tube

seal in it is how to get the entire interior of the tubing coated.  Then

drain out the excess.  Just about the only welds that won't be hollow will

be if there are any welds to flat steel.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Apr 27, 2009 8:59 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

For the powder coat fix up try to get epoxy paint the same colour as the

powder coat.  Marine shops have it in just about any colour you will ever

want.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

lcfitt(at)sbcglobal.net
Guest

Posted: Mon Apr 27, 2009 11:52 am Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

Noel,



I don't think I agree with this, at least as far as the Model IV Kitfox 

airframe is concerned.  I have cut out sections to modify certain areas and 

there are no through holes drilled to connect the tubing interiors.  Also, I 

have done welding to add tabs and if the tube was not predrilled at the 

weld, the heat would blow a vent  hole in the weld as the pressure buillt up 

inside the tube - each different tube.



Drilling to connect all interior spaces at cluster joints  might be 

preferred practice, but it was definitely not a practice when the Model IV I 

am building was jigged up and welded.  I would be happy to package up a 

small welded section that I cut out for you to inspect.



For current welding practice  I would definitely talk to the Kitfox factory.



Lowell



---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Apr 27, 2009 4:17 pm Post subject: Corrosion Prevention - 4130 Steel and Aluminum. What to use

All the frames I've been working on have been Super Cub and Aeroncas.  They

have all the welds not drilled but shaped so the weld is the outside of the

joint and there is nothing inside it at all.  Similar to the welds you will

se on "Orange County Choppers".  You will notice when they jig up a frame

tubing is always shaped on both sides before welding.  If they weld in a

cross piece they always cut their tubes to fit together exactly and then TIG

weld the joint so there is little warping.  The fitting part as I understand

it is the hard part of making cluster welds.  I don't TIG weld myself and

the work I do with the MIG I wouldn't trust to fly.  Evaluating welding jobs

was part of my training and several times We had a certified welder work on

planes at the AMO.  ( CDN for FBO ) 



No need to package up the welded section but can you post a few pictures of

it?  I'd appreciate that.  If they are large files send them direct to

noelloveys(at)yahoo.ca 



Noel



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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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