Polished Aluminum Clearcoat Secret

A. Hi Smitty. Anodizing is probably impractical under the circumstances, so you should pick a clear coat. Protectaclear from Everbrite [a finishing.com supporting advertiser] from Everbrite is a thin single-component clearcoat that you could probably add to every couple of years. Brass lacquer is designed to be stripped and repeated every few years. Two-component automotive clearcoats will probably work well enough. And several clear coats have been suggested by name here over the years.

Luck & Regards,

A. Hello Joe; hello Michael.

Remember that there are countless grades of aluminum, and some are optimized for clearcoating while others aren't. If the part was originally clearcoated or clear anodized, it's probably a good alloy for brightness; but if you stripped paint off of it, it's probably an alloy that wasn't intended to retain brightness and doesn't do as well.

It isn't easy picking a clearcoat either. If one coating was manifestly superior to the others in broad ways over a broad spectrum of conditions, the other 999 would have been off the market in short order :-)

Bright dipping plus anodizing isn't for the do-it-yourselfer, but it is what was done on aluminum bumpers, and tens of millions of streetlight reflectors, and may be what was done on those bikes originally -- it is available from plating/anodizing shops. Good luck.

A. Por-15 Clear, amazing stuff.
You can buy it online too [adv: Por-15 2k Clearcoat on eBay or Amazon [affil links] ; it's pricey but worth it. Clear powder coating can be good too, but it can be too thick a coating sometimes.

A. The Por-15 Glisten ⇩ has worked VERY well for my polished and brushed aluminum pieces. Is is very durable.
Understand, it is not 100% clear, so the metal takes on an ever-so-slight haze.

A. I've been researching this for a while. I've tried the Glisten --^, and yes it does add a haze. It's also prone to runs.

I've heard raves about Permalac [adv: Permalac on eBay] and Imron [adv: Imron clearcoat on eBay] . Eastwood has Diamond Clear.

VHT is said to have a good clear ( ⇦this on eBay or Amazon [affil links] ), and then there's always Zoopseal ⇩.

I'm looking to clear coat some polished brass, and will likely go with the Permalac for that. We'll see how it goes.

Ed. note: ZoopSeal no longer exists under that name; its inventor now calls the product ShineSeal ⇦this on eBay & Amazon [affil links] . Adam obviously has no axe to grind since he mentions 6 different products, but to the extent practical, please try to suggest TYPES of products: lacquers, epoxies, polyurethanes, single component, 2-K/2-Component, etc., rather than brand names or sources (huh? why?). This is a "no-registration" site, and honest appraisals by actual users are becoming overwhelmed by hawkers pretending to be satisfied customers of their own products and dissatisfied with competitive products :-)

A. I used a product called Everbrite [a finishing.com supporting advertiser] on my polished aluminum valve covers, applies easily, no runs, & has held up very well. I have no affiliation w/them, just great results.
Fred

A. Hi Jeff. It's hard to confidently say that chromate conversion coating will help the black spots specifically -- but it should be done anyway for better adhesion, corrosion prevention in the event of a scratch or pinhole, deterring filiform corrosion, etc. Powder coating should not go directly onto bare metal, but onto pretreated metal. Good luck.

Regards,

A. The Black spots are obviously contaminants.
I would think that they are possibly soot particles from incomplete combustion in your cure oven.
You can tune your burners to reduce or eliminate the problem from recurring.
You could "paint" your oven walls with odorless fish oil to decontaminate what is already swirling about.
Otherwise it could be just powder contamination from prior jobs in which case the "painting" option is still a winner.
Hope this helps.
Regards,
Bill

A. There is also a possibility that it is coming from the extrusion lubricant that has become imbedded in the metal.
I would run a test sample of wrought aluminum to see if it the oven or the aluminum.

A. Hi Kelly. The amount of flexing on an aluminum bicycle frame should be no challenge for a properly adhered paint or clearcoat. But you might look for an aluminum pretreatment before the clearcoat if you're going to use a hard 2-K clearcoat; you can probably successfully do a lacquer or single component clearcoat directly on your polished surface as long as it's spotlessly clean. Good luck.

Regards,

A. Hi Fernando. I am not personally familiar with clear chromating of aluminum being used to try to maintain its shine (which is not to say it won't work to some degree).

But it seems to me that the main issue is that a mirror finish is not going to last long without some type of preservative anyway because aluminum oxidizes instantly and fades quickly unless you are describing a component for high vacuum application or enclosed in an inert atmosphere. Must the surface remain electrically conductive? Because the usual way to preserve a mirror finish, done on countless millions of reflectors, is a thin layer of anodizing -- but that's non-conductive. You can see that we have added your question to a thread which covers others methods like clear coats, etc. Good luck.

... but please do me the favor of describing what the component in question is, and where it is used, because as soon as the questions become abstract, and the replies therefore have to involve a half dozen ifs-ands-&-buts, it makes for more work than most readers want so they don't reply, and tends to end the discussion :-)

Regards,

A. Hi. Thanks for the clarity of your reply. Although chromating is usually quickly dismissed as having "no dimensional effect", when it comes to a requirement for a sealing surface, I'm not familiar enough with the possible effect on surface finish to hazard a guess as to whether chromate conversion coating can effect a waveguide seal. Further, it does interfere to some extent with conductivity. MIL-DTL-5541 [on DLA] describes that conductivity effect in detail. Hopefully now that the issue is very clear, a reader who is familiar with such an application will respond.

Regards,

A. Hi Viney. I'm not sure exactly what your question is :-)

Are you looking for a shop to clear coat the parts for you, or a suggestion of what clear coat to use? Or are you unhappy with the result of your steel shot blasting process and want a better process? Are you achieving a bright polished look by blasting but afraid that the chromate conversion will spoil it?

More words please, but meanwhile I would be concerned that blasting with steel shot increases the likelihood of rust developing on your aluminum.

Luck & Regards,

A. Hi Thomas. Alodine is a Henkel trade name for a series of chromate conversion coatings for aluminum. It is not actually for "cleaning the surface", but for pretreating it after cleaning.

Although chromate conversion coating is the ideal pretreatment for aluminum in terms of corrosion resistance and insuring good adhesion of subsequent coatings, Alodine 1201 is a colored chromate and will impart a yellowish/goldish tone; it will no longer look like bare or polished aluminum. There are clear Alodines ⇦this on eBay or Amazon [affil links] which would be better.

I think your choices would be to find a shop who can do a clear chromate for you and see whether that's clear enough, or to skip the chromate conversion coating.

Luck & Regards,