taiwanluthiers Posted March 11, 2016 Posted March 11, 2016 Anyone know what chemical composition is alodine? In case you don't know alodine is a chromate conversion finish for aluminum. It turns aluminum into gold color (or no color, depending on type of product used) which imparts corrosion resistance but more importantly, it allows the aluminum to be painted or glued. I can buy it, but it's really expensive (more than 30 dollars per ounce) and from my understanding it's just some acid and dichromate... and I got some potassium dichromate so I just wonder if I could mix up my own. I suspect it works like passivating magnesium with dichromate...
Fulmen Posted March 11, 2016 Posted March 11, 2016 I've only done chromate on magnesium, and as far as I can remember that was straight CrO3. Nasty stuff. A quick search suggests that chromate on aluminum uses nitric acid as well as fluorides. I suspect you could formulate a working bath from dichromates as well, but it will take some Google-fu and experimentation. Can I ask what it's for? As far as I can tell the only real benefits over anodizing is electric conductivity and cost, so for home applications anodizing might be simpler.
taiwanluthiers Posted March 11, 2016 Author Posted March 11, 2016 I got some errors on some aluminum part that I have been trying to fix, and I tried epoxying aluminum plug in and it would not hold at all... so I read if I treat the aluminum with alodine the part would adhere better.
Mumbles Posted March 11, 2016 Posted March 11, 2016 The MSDS, which are everywhere, give a good idea to its composition. They generally are comprised of chromic acid, fluoride source(s), and potassium ferricyanide. The exact components and proportions will depend on which product you need. There look to be at least half a dozen different products under than brand.
ExplosiveCoek Posted March 11, 2016 Posted March 11, 2016 It's a product from one of of my competitors, it does indeed contain exactly the substances as mentioned above and does what is mentioned above. However the adhesion of epoxy paint should already be sufficient after degreasing and maybe sanding (this is what we do chemically normally, etching with an acid and fluorides) the aluminium.For degreasing just use an organic solvent and a rag or something. The product you mentioned is a conversion layer to give it extra corrosion resistance and better adhesion to coatings/paint. However I do not advise to do this at home, you still need to prepare the aluminium properly, this is the biggest step towards good adhesion, not only the conversion layer. Furthermore you'll have Cr (VI) waste. My advice would be to just let a professional do the job, most of the time their quality is much higher than one can do just in their garage box. Besides that, the price you're paying is way too high .
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