Topic: Best clearcoat or protectant for Polished Aluminum? Like the factory used...

[Tim2005]

I wish I knew what Honda used on the polished covers.  Worked well for a long time.  But, it probably doesn't matter.  I doubt the governments federal or state EPA guidelines would allow you to obtain it anyway.  It's important to note that Honda's covers weren't highly polished for a reason.  They were satin or brushed finished because those surface conditions allowed the coating to grab onto the surface.  Putting an organic coating such as paint over a highly polished surface often results in failure as the coating comes off in sheets.

Leaving the polished aluminum without a coating means that you will have to re-polish in the future.  The frequency of the polishing effort will depend and the atmosphere the surface is exposed to and the alloy composition of the aluminum, in particular, the copper content.   A dry, cool climate will increase the polished surface longevity.  Warm, humid climates cause rapid dulling and the need for repeat treatments.  Atmospheric impurities also have a negative effect on maintaining surface polish.  If you have acid rain, ocean salt spray, or airborne chlorine from a nearby pool or water treatment facility, you can expect surface dulling to occur at a faster rate.

The squiggly line corrosion, to which Rookster refers, is called filiform corrosion.  It occurs under coatings that have had poor surface prep, and/or microscopic coating pores where atmospheric contamination and humidity have reached the aluminum alloy underbase.  It is not generic to a clearcoat, but can certainly occur with such a coating.

If you can still get clear lacquer where you live, I can definitely advise against its use.  It will yellow with age and stands up poorly to the sun's UV light spectrum.


Cheers,

I'm sure I read somewhere that the stock finish was achieved with a belt sander then a coating of cellulose clear laquer, which would make sense as those would both have been common mass-production options in the 70s. It does get baked on incredibly well over the years too, doesn't it! Nowdays, having tried all forms of finish, I prefer to go with polished bare metal and then just give it a quick going over with Brasso every couple of months. It somehow looks "right" like that. It also eliminates any problems with stonechips, cracking around bolt heads, spanner scratches etc - you  can just polish them out.

[Kikemon]

Hey 736cc - Aren't ceramic coatings used on ehxaust systems as insulators to reduce heat loss through headers and increase performance? On a bike that is a rider, not a show bike, would the reduction in heat shedding due to the coating be significant enough to cause longevity problems?

[736cc]

Not a problem

[TwoTired]

Can you ceramic coat in black, as found on the F2s?

[736cc]

Satin black

[Jonesy]

The big issue with putting a coating on aluminum (as TwoTired already pointed out) is getting the finish to adhere well to the surface. Even when aluminum looks clean and shiny, there is actually an almost invisible layer of oxide on the surface. The paint will adhere to this layer of oxidation, when you really need it to grab the aluminum itself. This is typically why aluminum surfaces usually need to be painted with self-etching primers that contain a mild acid that eats through the oxide layer.

I was advised by a paint specialist to wash down aluminum parts with mild phosphic acid to etch the surface, wash them thoroughly with water and then dry them off completely. Paint or clearcoat immediately after.

[Loas 78 CB750K]

So Jonesy, I take it that by using an acid and then clear coating you can get polished aluminum to keep its shine like chrome