Darkening after polish

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bcgreen

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I was wondering what causes alumin. to darken after using a polish?
I did a set of alumin. wheels and it caused some worry on my part, but I was able to get the polish off and get the desired chrome like finish.
 
looks like the polish has reacted with it. aluminium can be funny stuff. did the polish say 'suitable for use on aluminium' on the container? if not, id suggest looking of one that does
 
Niblick said:
looks like the polish has reacted with it. aluminium can be funny stuff. did the polish say 'suitable for use on aluminium' on the container? if not, id suggest looking of one that does
Click to expand...

This is from Mike P. and another chap, Todd Helme, when he did the bed of a truck. The alumin. in the whole bed of the truck was dark.



54.jpg
 
bcgreen said:
I was wondering what causes alumin. to darken after using a polish?

I was able to get the polish off and get the desired chrome like finish.
Click to expand...
The "Darkening" is probably a mixture of the remnants of the passivation coating...Aluminum oxide...and those of the polish/compound.

Bob
 
Hmm... I always thought it was the "real" color of the aluminium underneath, once the al. oxide has been removed from the surface.

Interesting to hear other views / facts. :)
 
Aluminum oxide is white, which is why the unpolished section appears chalky. Essentially, that is how aluminum "rusts". Unlike iron rust though, aluminum oxide builds a layer that protects underlying aluminum from further oxidation over time. Iron oxide is very porous and allows more oxygen to reach bare iron, which is why the process continues until all the iron eventually becomes iron oxide.

The polished side is oxidation free so you don't see the effects of looking through the top layer of oxidation down to the reflective aluminum. At least that's my theory.


Looks like the shiny side of the foil to me.
 
I did think that initially, but it looks just a bit too dark tbh. Might just be the way it's lit of course
 
Setec Astronomy said:
...Or bringing out the "color" as they would say in the metal buffing industry.
Click to expand...

Perfectly polished aluminum colors well. It is one characteristic of the process that sets my rig apart from the other hundred or so parked on the line. Chemically brightened aluminum doesn't color and is usually streaked.

Also, IMO, colored metal tends to retain the bling for a longer period of time than chemically brightened metal.

bcgreen said:
... but I was able to get the polish off and get the desired chrome like finish.
Click to expand...



Parked side-by-side at the shipper, my Alcoas more closely resemble a chromed look than aluminum when viewing the chemically treated wheels parked beside me.

Even after a 600 mile trip throught salt and what not.
A simple rinse to remove the grit, a light wash followed by patting them dry, the end product still looks like chrome.
 
Hand cut and hand polished viewed in natural sunlight.





Polished with an air die grinder/buffing wheels supplied by glad hand air line.

Hand polished/cut to about 70% correction

 
Actually, IIRC, the above DEF Door was cut by hand. Somewhere about 11 hrs in DEF door alone. Over thirty hours on doors and step threads over labor day wknd in Harrisburg, Pa. I was hoping to use Tuscarora Dave's shop and my pro products and tools but the tractor trl combo would disrupt his business.

I was assigned 12 different tractors during my time at this co. All received love. Several blinged out and paint polished/coated.

Photos of DEF door done by die grinder/liquid OTC polish











Can't get the CHROME look without the "coloring"
 
bcgreen said:
I was wondering what causes aluminum. to darken after using a polish?
Click to expand...

It's normal.

It's not so much darkening but more of clearing up or clarifying to show the natural brilliance. I can show you this same effect on my aluminum leg.


For the record, this was an epic transformation that Todd and I knocked out... I just ran into the owner of this truck last weekend for the first time since we buffed out the aluminum diamond plate bed. Sad to say he sold the truck.



Diamond Plate Aluminum from Dullsville to Mirror Shine on a 1947 Chevy Pickup


Dullsville
DiamondPlate002.jpg




Mirror Shine
DiamondPlate004.jpg




:dblthumb2:
 
WE also buffed out the paint on this truck and there's a live video recording of the project.


Live Video Broadcast - 1947 Chevy & 1986 Porsche 928 - Extreme Makeovers

1947 Chevy & 1986 Porsche 928 - Extreme Makeovers

[video=youtube_share;afVpsE8qC4w"]1947 Chevy & 1986 Porsche..."...[/video]​



And you can find all the before, during and after pictures for this truck on page thread of this thread,

http://www.autogeekonline.net/forum...evy-1986-porsche-928-extreme-makeovers-3.html


DoubleTrouble032.jpg


DoubleTrouble035.jpg


DoubleTrouble036.jpg


DoubleTrouble033.jpg


Luckily there's pictures for all the cars that have gone through Autogeek's Show Car Garage or I'd forget about them...


:D​
 
Vegas Transplant said:
Perfectly polished aluminum colors well. It is one characteristic of the process that sets my rig apart from the other hundred or so parked on the line. Chemically brightened aluminum doesn't color and is usually streaked.

Also, IMO, colored metal tends to retain the bling for a longer period of time than chemically brightened metal.

Parked side-by-side at the shipper, my Alcoas more closely resemble a chromed look than aluminum when viewing the chemically treated wheels parked beside me.

Even after a 600 mile trip throught salt and what not.
A simple rinse to remove the grit, a light wash followed by patting them dry, the end product still looks like chrome.
Click to expand...
OOOPS!!! I misread the OP's query...
thinking he was asking about the darkness-discoloration
of the "removal-cloth".

Thanks for the clarification, VT! :props:

Note:
I like it when my chrome wheels have that
tinge-of-blue coloration. :)


Bob
 
Mike said it best, but I also know that different grades of 'rouges' and extended last step buffing intervals yield varying 'color' end product.

Finishing with a 10" buffing wheel used at high rpm without product for an extended period of time yields the best end product IMO.

Interesting to hear about the 'blueness'.
Something new for me to look out for. My idiosyncrasies are more numerous than I'd like to admit.

Hoping that you and Miss Cora are keeping warm. I've been arms length from Mom these past few days as I while away on the forums.

:cheers:
 
Note:
I like it when my chrome wheels have that
tinge-of-blue coloration. :)
Bob[/QUOTE]

Its more of a gun metal gray look. On my vehicle it was not attractive, so now I am careful on application so I get more of the chrome look.
 
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