Painting aluminum

[boatnut74]

I know there are several threads out there about this but they don't answer all my questions. I will be painting my boat soon, it's stripped down to bare metal and I will scuff with red scotchbrite. Is it absolutely neccessary to use alodine? What are the downsides if I don't. What's the difference between zinc chromate and self etching primer? I know the zc is some pretty nasty stuff. I will be using Rustoleum for primer and paint I just want to make sure I have a good base for it to adhere to as I don't want to do this again. Any other advice would be great also.

 

[MichaelP]

Re: Painting aluminum

I've been looking into this myself. The plan was to go with alumiprep, alodine then ZC but run into snags. First off the alumprep and alodine are very nasty chemicals and I don't want to risk getting chromium in my dug well so I found this PreKote product that I'll try...http://www.aircraftspruce.com/catalog/cspages/preKote.php

I also learned that ZC primer can't be brought into Maine so now I'm looking for a etching primer in quarts with little luck. I'm thinking about simply going with the Sherwin Williams top coat system on top of Prekote. At least I'd have a good choice of colors and its supposed to be as good as Rusto.

 

[Woodonglass]

Re: Painting aluminum

This has been Highly Debated here on the forum.
You will NOT get a definitive answer. YOU will hve to make your OWN FINAL decision. Each member has done what THEY have thought best for their given situations.

This Sticky At the Top of the Forum has some GREAT information.
http://forums.iboats.com/showthread.php?t=457159

I have had luck with the following.

Final WET Sanding with 180 Grit
Wash Down with 50/50 mix of White Vinegar and Water.
Prime with Rustoleum Self Etching Primer
Paint with Rustoleum Professional Oil Based Paint using the following formula.

1 qt paint
1/2 cup Acetone
2 oz Valspar Acrylic Enamel Hardener (Sold @ Tractor Supply)
Applied using the Roll n' Roll Method. (If Spraying thin with 2 Cups of Acetone and use HVLP Gun with 1.8mm Tip)

Fellow iBoater lakelover used the above with great results.
http://forums.iboats.com/showthread.php?t=309879&highlight=lakelover

 

[ezmobee]

Re: Painting aluminum

Prime with Rustoleum Self Etching Primer
Paint with Rustoleum Professional Oil Based Paint using the following formula.

Hey Wood, can you go right over the etching primer with the top-coat? I was thinking you might want to hit it with a coat of Rustoleum Clean Metal Primer over the etching. Perhaps that's completely unnecessary.

(However if you want some build to maybe fill some scratches and what not, I can't imagine it would be a bad idea to add this step. Thoughts?)

 

[Woodonglass]

Re: Painting aluminum

Either Way is Fine. Using the Metal Primer WILL as you say have the effect of filling some scrathes and small dents but the Paint will adhere to the SE primer just as effectively as it will to the CMP. Good Catch though EZ. I will include that in my further Recommendations.

 

[MichaelP]

Re: Painting aluminum

I think If seen that somewhere before.

Besides the issues I've listed above I also have a corrosion issue to address and a cover up or a cleaning won't last. More details on my resto thread.

 

[boatnut74]

Re: Painting aluminum

So it looks like I won't need the zinc chromate, just the self etching. I'm just looking for a durable finish that wont peel from bad adhesion. I'm working with to much square footage to want to do this a second time. If anyone else has some good experience, or bad experience with certain products I would love to hear it!!

 

[Yacht Dr.]

Re: Painting aluminum

I know there are several threads out there about this but they don't answer all my questions. I will be painting my boat soon, it's stripped down to bare metal and I will scuff with red scotchbrite. Is it absolutely neccessary to use alodine? What are the downsides if I don't. What's the difference between zinc chromate and self etching primer? I know the zc is some pretty nasty stuff. I will be using Rustoleum for primer and paint I just want to make sure I have a good base for it to adhere to as I don't want to do this again. Any other advice would be great also.

Hello BN ..

Here is the low down on Alum and prep for paint..please read this posted from a member here.. http://forums.iboats.com/showthread.php?t=457159

The Alumiprep ( http://www.aircraftspruce.com/catalog/cspages/alumiprep.php ) is a cleaner for alum and explained in the above thread..

You can sand dry or wet .. I like Dry sanding for prep before Alumiprep..

So you have your Alum nice and Clean/Converted to accept a primer ?? um..not so Fast there ..

At this point all you have is a nice Fresh Alum Surface to do the next step ( you prepped your alum to accept compatibility for the next coating ) .. at this point you dont have some kind of Magical "coating" on your alum .. its just CLEAN as Clean can get ..

So now lets say you take my advice and buy the AP33 and wash down your boat .. now you think its time for some kind of "self etching primer" ... hmm..

Alodine ( http://www.aircraftspruce.com/catalog/cspages/alodine1201.php ).

At this point you have Raw Clean Alum .. and now you want to prime..but is your Primer coat compatible with Clean Freshly sanded Alum ?? or .. Did you Alodine it ..

The Alodine is basically a a thin "tie" coating that bonds to your alum and accepts certain Primers .. ( not all primers ).

Zinc chromate is the standard primer for salt water applications ( masts etc. ). ZC is not always applied ..

Primers are Always applied to Alum applications .. some are ZC .. while others are epoxy based ( 545 etc. ).

Raw alum should take special care on the process and timetables of the job .. Its a Bang Bang thing ..

YD.

 

[boatnut74]

Re: Painting aluminum

Thanks YD. Reading through the Starcraft restorations I haven't seen anyone who used alodine, thats why I was curious. I don't plan on being in any saltwater, but it could happen someday. I have been wondering the process Starcraft used for painting these boats as it seems all the old paint was very well adhered but I felt better stripping it off anyway. Under all the old paint is very smooth which makes me wonder how they got the paint adhered so well.

 

[Yacht Dr.]

Re: Painting aluminum

Alumiprep is a "cleaner". Some use vinegar etc..its just a cleaner/conditioner for your primer

Alodine is a "Tie Coat" between raw alum and the primer ( Alodine Loves alum ..and loves primer ). Its just a Tie coating.

You can try the Self etching primer coats .. I dont/cant risk the tie coat/primers .

Other then what the link I gave you with pics I cannot verify any other methods used nor there long term outcome of flake issues ..I can for sure say the link gives you a pro point of view ..

Paint over raw alum .. not a good idea IMO ..
Paint over some Self-etching primer .. Risky.. doable some say . I cant verify that procedure ..

YD.

 

[boatnut74]

Re: Painting aluminum

So after I prep with alumiprep and apply the alodine, do I need to shoot a coat of primer right away after drying? Or can I leave it for a week or so and come back and shoot the primer.

 

[jtrom]

Re: Painting aluminum

Great information here....Do you normally use more than one coat of the self etching primer ???? ( if using woodonglass's method)

 

[ezmobee]

Re: Painting aluminum

Great information here....Do you normally use more than one coat of the self etching primer ???? ( if using woodonglass's method)

No. You really only a need a light dusting of the stuff.

 

[Tahorover]

Re: Painting aluminum

Alumiprep is a "cleaner". Some use vinegar etc..its just a cleaner/conditioner for your primer



YD.

Vinegar is too weak to do anything after the recommended dilution. If the user has any kind of alkalinity in there water, the solution will be neutral Ph or so weak it it's a waste of time and effort.

Alumiprep has a nice slug of Phosphoric acid:
http://www.chemical-supermarket.com/files/Henkel Alodine Conversion Coatings/Alumiprep 33, MSDS.pdf

 

[Yacht Dr.]

Re: Painting aluminum

So after I prep with alumiprep and apply the alodine, do I need to shoot a coat of primer right away after drying? Or can I leave it for a week or so and come back and shoot the primer.

Once you start your Cleaner and conversion coatings dont stop until its primed.

A flipped over tinny will not take that long for the Alumiprep+Alodine.. dry off with wipes or Air ( 30min-1 hour depending on size ). When your Ready to prime you do the AP and Alo ..then Prime Full coatings. I dont know why you would want to condition your Alum and then wait a week to prime.

Great information here....Do you normally use more than one coat of the self etching primer ???? ( if using woodonglass's method)

Yes .. When not using AP and AD .. ( But that was years ago and I dont do the self etching primers anymore on alum .. other metals could get by ). I dont mess around with Alum. I do it Old school .

No. You really only a need a light dusting of the stuff.

Sure about that EZ ? Sand clean with Vinegar and light dust with SEP then no-sand Paint on the primer will hold ? ..
Just wondering ..

Prep first .. then Condition the Alum .. then Prime. No reason to Self etch if you did AP and AD + good primer for paint.

OutDrives are a bit different..you want to Prep/ZC/Base/clear all in one step from what our tech said ..Small stuff..

YD.

 

[boatnut74]

Re: Painting aluminum

So.. the best way to do this from my understanding would be
1- scuff surface
2- clean with alumiprep
3- apply alodine, rinse well and dry
4- spply primer (zc or a 545 epoxy?)
5- filler primer
6- top coat

Just covering my basis here as I want to do this right.

 

[Yacht Dr.]

Re: Painting aluminum

So.. the best way to do this from my understanding would be
1- scuff surface
2- clean with alumiprep
3- apply alodine, rinse well and dry
4- spply primer (zc or a 545 epoxy?)
5- filler primer
6- top coat

Just covering my basis here as I want to do this right.

IMO.. yup ..

Dont miss the windows From AP to AD to primer .. after the Primer goes on..then you can relax..after the prep of the primer/topcoat is done your in the next hurry to get the top coat on ASAP.

The best way .. IMO ..is what you described here ..

YD.

 

[boatnut74]

Re: Painting aluminum

I have a buddy who used to paint aircraft so he's worked with the alodine and such before. I'm sure he would help me get it to the primer stage. I'm working with alot of square footage so an extra set of hands would sure be helpful. Thanks again.

 

[luckyjr]

Re: Painting aluminum

i was going to paint. But, I am going to blast them with baking soda now and use aluminuma Gaurd.

 

[boatnut74]

Re: Painting aluminum

How much alodine would it take to do my 22' boat below the rubrail? Would 1 gallon be sufficient?