Alodine and Alumiprep

[JanRV6UK]

Originally Posted by BillL

Where is your data that a self etch primer provides corrosion protection for 2024 in a salt spray booth with a scratch test.

Hi

It all depend on the etch primer you use ... http://www.paintservices.com/pr30b-etch-primer/

That etch primer is excellent alternative to Alodine. But may not be available in all parts of the world .. as it contain lots of not so nice stuff .. as far as your lungs are concerned :-) ... But .. look at the standards it conforms to... Any other etch primer that conform to the same standards will works great as a primer against corrosion ...

[AusFlyingBear]

Thanks everyone for the comments.

Originally Posted by rvbuilder2002

I was assuming the OP meant bypassing priming for all interior substructure?

Yes I was only planning on the substructure. Haven't decided on whether to paint or "wrap" the outside yet...still a away off.

Thank you Bill, will take note of the cleaning.

Originally Posted by BillL

Hi Ian,

Through some experimentation of my own, it appears to be a cleanliness issue.

I dip my parts, so let's start with that. I clean the parts with mineral spirits to get sticky stuff, and then wipe with a wet towel of alcohol. Denatured or rubbing (ethyl or isopropyl) all over. On small parts without label adhesive, acetone works too. I just don't like the smell. Dip in prep solution for 2-3 minutes, rinse in distilled water (sometimes just spray down small parts with hand sprayer), then dip in alodine for 2 1/2 minutes - or longer if weak to match colors. Rinse in new water, blow dry with shop air and hang for 24 hrs. That cured my mottling. Try these on your own for a starter.

Any other cleaning process you want to ask about - I probably tried it. Many worked but this seemed to must efficient and I stopped experimenting. Plastic buckets, 3" PVC tubes (vertical), and large plastic storage containers have been used.

Last thing - I had some corroded 2024 .063 and it looked pretty bad. It needed some scotchbrite to level the surface, then the other steps left a nice finish.

[BillL]

Originally Posted by JanRV6UK

Hi

It all depend on the etch primer you use ... http://www.paintservices.com/pr30b-etch-primer/

That etch primer is excellent alternative to Alodine. But may not be available in all parts of the world .. as it contain lots of not so nice stuff .. as far as your lungs are concerned :-) ... But .. look at the standards it conforms to... Any other etch primer that conform to the same standards will works great as a primer against corrosion ...

Fair enough, Jan. The tech data sheet looks like this is a what we would call a wash primer, and still needs a zinc/strontium chromate epoxy or urethane primer over it. Commonly in the US an etch primer is for automotive steel and does little or nothing for the 2024 aluminums. Too bad we (me) learn all the really good factual stuff at the end of the build! Maybe on the next one . . .

[JanRV6UK]

Originally Posted by BillL

Fair enough, Jan. The tech data sheet looks like this is a what we would call a wash primer, and still needs a zinc/strontium chromate epoxy or urethane primer over it. Commonly in the US an etch primer is for automotive steel and does little or nothing for the 2024 aluminums. Too bad we (me) learn all the really good factual stuff at the end of the build! Maybe on the next one . . .

Yep ... it is what I enjoy about this building stuff ... learning new things .. and hopefully not have to make to many parts in the process .... I think by the time I am done, I will have made 3 ... at least parts for 3 aircrafts :-) !! ..

The primer I am using does contain chromate and does not need a separate epoxy primer - you are absolutely right that many generic etch primers are not suitable for aluminium and will require a top coat to seal it, and have no anti corrosion properties for aluminium. I could use this : PR 143 epoxy primer - from the same company - on top of the etch primer I am using now ... but I think that would at least for all interior be an overkill (and add more weight) - May do it on the outside, before top coat. Yes the etch primer is a wash primer .. very light coat ... but what is great about it .. as I said earlier it has anti corrosion properties and does not absorb moisture, hence no need to overcoat it ... unless you want ever better protection ....

Still very important to fully clean and degrease before you apply it (as is needed for Alodine as well) - In the US you tend to use Alumiprep 33 which is ideal to get the alu ready for etch priming (or Alodine) .. In Europe and the far east - maybe Australia as well ..?? This stuff is great DEOXIDINE 624 ... does the same as Alumiprep 33

No wonder they call it Primer war !! :-) ... so many options ..!