Aluminum metal pretreatment.

[Rick!]

Have you called the plater and ask what etching/cleaning baths he runs prior to the plating dunk?
Typically, the etch baths would remove any surface oxidation, in my experience.
Aluminum basically starts to build its oxidation layer immediately, like when you start blowing off the blasting dust prior to applying Alodine.
Also ask the plater whether he wants alodine in his etching baths or just raw aluminum with a light oxidation.
As long as you're not shipping over salt water, you shouldn't have much issue.

[dfarr67]

I don't see how a plater has anything in common to what I'm doing? I don't have bathes either.

[hoodeng]

I spoke to a friend that has a powder coating plant, his advice is as follows.

Get in touch with whoever is going to be your consumables supplier, they will advise on different material/ surface pre-treatments and processes if you are not sure on choice of products and finishes you are trying to achieve.

One pre-treatment for steel is the chemical in the photo, he also said some materials have applied coatings on surfaces already, some require light scouring others more extensive preparation, this also includes alloys, ferrous and non-ferrous. Previous coating stripping and light blasting can be required as well.
One thing he said was paramount was that once the surfaces had had the final preparations was that you do not handle the surfaces afterwards.

Cheers.

[David Redszus]

For aluminum, Alodine is suggested as a surface prep for coating or painting.

For ferrous metals, manganese phosphate or zinc phosphate is suggested as a surface prep.

[dfarr67]

For aluminum, Alodine is suggested as a surface prep for coating or painting.

For ferrous metals, manganese phosphate or zinc phosphate is suggested as a surface prep.

I wanted to move over to the topic of ferrous, as with the other chem- fresh after clean/blast I want to mist a chemical on at room temp and let dry with no need to wash later. Been looking at Picklex-20 but I suspect I'm not alone in thinking they are gouging on price, looking at Ospho (Caswell plating supplies this), POR-15 MetalPrep, FlashGuard looks good but I to buy 5gallons which is $$ for me. Any other suggestions?

And yes- skin contact is a nono after cleaning.

[HDBD]

David, how would an intake or other die cast engine part appear after the alodine treatment assuming it was glass beaded first? Besides sealing does it change the appearance? TIA

[dfarr67]

There is two versions of alodine- a clear treatment and one that leave a tan colour, for me with powder coating I intend to cover with a solid colour so it doesn't matter.

[David Redszus]

David, how would an intake or other die cast engine part appear after the alodine treatment assuming it was glass beaded first? Besides sealing does it change the appearance? TIA

Alodine comes in clear or yellow. If the yellow treatment is allowed to remain in contact with the aluminum for an extended period of time it will become almost olive drab in color. If the treatment period is limited, it has a golden irridescent color.
The darker the color, the more protection is afforded as is often used by aircraft.

The actual color will depend on the alloy of the material. Die castings often contain zinc which changes the color.
If appearance is important, testing will be necessary.

For aluminum, the procedure that I have found best consists of:
degreasing and carbon removal
bead (not sand) blasting
alodine treatment
clear Cerakote finish