alodine or zinc chromate?

[loop]

or both. I already have both from previous projects.
painting a mid ,swivel and clamps. its all bead blasted to bare aluminum. just wanted to know the best way to go.
Also,what is a good paint. looking for something "off the shelf " that wont cost a fortune for a one time paint job. Would the Interlux Perfection 2part work good for this. It will be all black and I will be spraying it. Of course the cowl will be painted with the same paint too.
Thanks

[4JawChuck]

Alodine first to convert the surface, your primer second (Zinc chromate is OK) to prep the surface and provide a adhesive substrate for the paint then your top coat. Many people have skipped the primer coat with excellent results but coverage and show through can be an issue with lighter color paints. If its black your shooting you could likely skip the primer but it adds thickness and texture to the final coat so the visual results with a thin top coat may not be as nice.

In general you can shoot top coat right on top of alodine as long as its is dry and baked or aged, the baking/ageing process helps develop the conversion coating thickness in the presence of air. If you can't bake a week in open air is sufficient.

[Dave Strong]

Be careful with the Zinc primer, I didn't read all the info and the have a time frame when it is best to topcoat. I waited to long and the paint did not stick well.:rolleyes:
Dave:smiletest:

[sschefer]

Zinc Chromate is poor mans Alodine. Alodine is a chromate conversion process. The problem with Alodine is being able to apply it correctly. Not an easy proposition unless you have a lot of patience and perserverance. 1201 is what we think Merc uses on the Saltwater and some of the HiPo motors. 1500 is clear and not quite as effective but perfectly fine for a fresh water motor if you stay out of Alkaline lakes. It requires the same preparation but your imperfections don't show up and you can leave either 1201 or 1500 unpainted if you want.

Once Alodine has been applied, no further prep is need before applying paint. I've stripped a few Merc blocks and there's nothing but Alodine and paint on them and it's a bear to get it off so it does work fine.

Zinc Chromate primer is not the best any time and definitley not for use with Interlux Perfection. That process requires Interlux primer and if you're gonna shoot it you need to warn your neighbors, wear a mask with an air supply and shoot it from a pressure pot. It is best applied using the roll and tip method but you can brush and tip also.. My advice.. don't even try it.

So with that said - forget the alodine it's a pain..Glassbead, wash with warm soapy water and paint it with Moeller Phantom Black engine paint. Mines been on for a year now and it still looks pretty good.

However, I don't plan to paint or alodine anymore. The aluminum will oxidize in about two weaks and form its own natural layer of corrosion protection. It won't stand up to salt but on a freshy it should be fine. Yeah, I know, I found that out after I'd gone half nuts getting 1201 just right.

[loop]

thanks to all for clarifying this.
I have always used zinc chromate in the past with good results but was wondering if there was a better way.
due to time constraints,I ended up using an etching primer and Moeller Phantom black as sschefer suggested. Experimented with quite a few rattle cans claiming gasoline resistance,. The Moeller paint was the only one that seemed to truly live up to it. Duplicor wheel paint (polyurethane) also seemed to work. Duplicolors etching primer is also fuel resistant and seems to have a good bond.
One surprise was Krylon Fusion. I had painted some atv plastics a couple of years ago. Gas didnt soften or dull it. Only after some hard rubbing with a gas soaked towel did I see any color come off. And it actually shined the paint.
Thanks again for all the info

[zx185]

alodine does convert the aluminum. before though you should use alumiprep, thats an acid etchant. start with a clean and dry part. pour it into a tub to soak the part if possible, your part will foam/bubble, you can just wear latex gloves, also a gray scotchbrite pad will help prep the surface. then rinse really well with water, but dont dry. . then you do your alodine. if you can, soak the part in the alodine for a few minutes. there are two types, one is clear, one is gold. the gold is nice becuase you know when the part has taken the alodine well enough. both steps you can bag the part as well. once it has taken the color, rinse with water, then wipe clean with alcohol and rags to remove the residue. now you can zinc chromate prime. these are the steps that need to be done, i work on aircraft and for proper corrosion control and paint adhesion, these are the best methods for aluminum. once your primer has dried, scuff with scotch or fine sand paper and your ready to paint any top coat.

[Bruster]

PPG DP epoxy primer with PPG Concept acrylic urethane single stage topcoat. 21st century technology.

[Riverman]

before though you should use alumiprep, thats an acid etchant.This is key, alodine won't work worth a damn without an acid etch first. Alumiprep contains phosphoric and hydrofloric acid, nasty stuff. Read the MSDS before using.