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topic 23481

Polished Aluminum Clearcoat Secret


A discussion started in 2003 but continuing through 2020

2003

Q. I am inquiring about polished aluminum, specifically the polished engine case pieces of 1970s motorcycles. I like to fix up these bikes as a hobby. My problem is identifying the clearcoat applied to these polished aluminum pieces. The clearcoat is so unobtrusive that a lot of enthusiasts do not realize it is there. In some cases the original Japanese factory applied clearcoat has turned to a yellowish color. Commercially available "Aluminum Clearcoat" products have proven unsatisfactory. What is the secret to coating polished aluminum with an extremely clear, long lasting protective application?

Many thanks,

Michael Waugh
- Decatur, Alabama


2006

Q. I am trying to find the best way to keep the aluminum parts on my motorcycle their mirror finish a long time and make them EASY to clean. I have tried many different things and I'm now ready to do whatever it takes to make them look show quality but very easy to maintain. I have heard of people using UV resistant clear coats. Any recommendations?

Joe Mergl
polisher - New Jersey


2006

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.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



2005

Q. We are using aluminum electrodes for electrical conductivity in instruments. Now we use it with buffing.we get the shine , but it does not remain constant and goes very bad soon. Kindly guide how to make aluminum electrodes mirror finish and long lasting.

Prashant kulkarni
Electronic Instuments - Nasik, Maharashtra, India


2005

A. Aluminum is a very active metal which oxidizes instantly. As you have found, the shine will quickly fade unless you successfully anodize it or clear coat it. Those methods, however, render it non-conductive. Short of plating it with another metal, a clear chromate conversion coating may be the only thing that will work, and I can't say how shiny it will stay or for how long -- just "longer" :-)

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2007

A. POR-15 Glisten [affiliate link to product info on Amazon], amazing stuff.
You can buy it online too; it's pricey but worth it. Clear powder coating can be good too, but it can be too thick a coating sometimes.

R Malm
- Ottawa, Ontario, Canada

----
Ed. note: This and subsequent replies seem to be referring back to motorcycle components because clearcoats are obviously not acceptable for electrodes.


March 28, 2008

A. The POR-15 Glisten PC 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.

Adam

Adam Streubel
- Appleton, Wisconsin


November 23, 2008

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

I've heard raves about Permalac and Imeron. Eastwood has Diamond Clear.

VHT is said to have a good clear (VHT Clear Coat [affiliate link to product info on Amazon]), 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.

Adam Streubel
- Appleton, Wisconsin

----
Readers: please try to suggest TYPES of products: lacquers, epoxies, polyurethanes, single component, 2-Komponent, etc., rather than brand names or sources (why?). This is a "no-registration required" site, so honest appraisals by users are often soon overwhelmed by spam and hawkers pretending to be satisfied customers of their own products and dissatisfied with competitive products :-)


September 15, 2009

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

Fred Ryder
- Haines City, Florida



Will chromate conversion coating stop black spots on powder coated sanded aluminum?

June 13, 2014

Q. I have a 6061 aluminum extrusion that we are sanding and applying a clear powder coat to, It looks as if sometimes the heat from the powder coat oven bakes something out of the extrusion and leaves black spots under the clear coat. Would Alodine help seal the part and stop this?

Jeff Hodgson
precision manufacturing - Champaign Illinois


June 2014

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,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


June 19, 2014

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

William Doherty
Trainer - Salamander Bay, Australia


June 20, 2014

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.

James Watts
- Navarre, Florida



December 12, 2014

Q. I have built a teardrop trailer and clad it with sheet aluminium. I wish to apply a clear coat to the surface and need advice. Thanks.

Ken Howes
- Windhoek Namibia



May 25, 2018

Q. I am Restoring a 1996 Cannondale R500 bicycles All Bare Aluminum. I polished it with Mother's Aluminum Chrome polish. But I want to protect this almost Mirror Finish with Clear Coat on a flexible frame. Is it possible?

Kelly Chipper
- Islip, New York, USA


June 2018

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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading



Conversion coating aluminum with a mirror finish

May 13, 2020 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I have an aluminum component that has a specific surface with a mirror finish. I want to know if Mil-DTL-5541 [link is to free spec at Defense Logistics Agency, dla.mil] can be applied on this surface or do I need instruct to mask to preserve the mirror finish.

Fernando Ortiz
- Plano, Texas


May 2020

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 it tends to end the discussion :-)

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


May 13, 2020

Q. Ted,
Thank you for responding. The parts in question are wave guides used in an antenna. There are two different components with two raised mating surfaces both having a mirror finish. Both components are mated and the mirrored surfaces produce a seal for the internal channel. The two surfaces need to remain electrically conductive.

Fernando Ortiz
- Plano, Texas


May 2020

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. Hopefully now that the issue is very clear, a reader who is familiar with such will respond.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

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