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Clear Anodized Aluminum Vs Aluminum

gabagoo

New Member
Customer gives me a spec sheet for a township and they are requesting pole signs 2" x 12" that are strapped onto the light standards. The aluminum is covered with high intensity reflective and black numbers. My regular supplier does not have clear anodized 1/16 of an inch and asked why we would use that over regular aluminum considering it never gets seen.... Is there a difference between the 2 for this given application? Your thoughts?
 

CanuckSigns

Active Member
You answered your own question Barry, it's a government spec!

My understanding is that anodized is better if you live near the ocean and have salty air, but we are a good 2000 km from the atlantic.
 

gabagoo

New Member
yea, this town is a good 1000 miles away from any salt water, but I think I will use enamel white
 

equippaint

Active Member
There was an older thread on here about a bunch of municipal signs that were delaminating because they were applied on mill finish aluminum to save a few $$. Id assume the annodized treatment would provide a bonding surface for the vinyl. An etch and alodine or etch and etch primer is whats typically used to make paint adhere, not sure with signs.
 
Correct Annodized and Alodine Coating are done to help the aluminum resist corrosion. Technically I believe all permanent traffic signage is supposed to be made with a Alodine or Annodized Coating. Both are very similar but Annodizing requires an electric current. If you buy blanks from Grimco they are Alodine Coated.
 
Might work for some. Maybe not for everyone though. Depends on the customer. I would imagine annodizing or alodine coating the aluminum gives an even longer lifespan though. It really shouldn't be that hard to find aluminum like that.
 

Joe House

Sign Equipment Technician
If your sign supplies distributor doesn't have it, look into sheet metal suppliers. You may get it past the inspector - or you may not. I'd hate to have to redo the job because I didn't take the time to source the material that was called out in the specs. I imagine that if it's in the specs, it can be found pretty easily.
 

signbrad

New Member
I'd assume the anodized treatment would provide a bonding surface for the vinyl.

This would be a good question to find an answer to.

When it comes to painting aluminum, an anodized finish can adversely affect the adhesion of a painted film. The Matthews Painting Manual, in its substrate preparation section, specifies that an anodized coating must be sanded off before Matthews products are used.

As many know, anodizing is a procedure for forcing the aluminum surface to oxidize evenly. The depth of the oxidization varies, which partly determines the cost of the finish. The oxidized layer then becomes a protective barrier that is stronger than a painted film.
Presumably, the anodizing makes it more difficult for an etching primer to bite, just as galvanizing does with steel, though the Matthews Manual doesn't specifically state this (I'm guessing).

When it comes to vinyl adhesion, does anodizing help or hurt? I'm sure there is information on this somewhere.

Brad in Kansas City
 

visual800

Active Member
Get you some white aluminum and placed a reflective laminated digital print on top.....DONE! Specify in your quote what they are asking for is ridiculous and in your experience you would do it this way

SPECS: Regulated BS from people that dont do the actual work
 

Johnny Best

Active Member
Regular mill finish aluminum has a oily feel to it and the anodized finish seals everything in and vinyl sticks to that a lot better. If you take regular mill finish and start to wet sand it you will see the black oilly like oxide substance come up you won't have that if it has been anodized, unless you sand down past it. But as suggested if you prep it right and paint it (using the right epoxy or zinc cromate primer and a good coating like Matthews and not a OneShot enamel finish, or rattle can paint from Home Depot) it will work fine and no one would see it anyway. But with the cheap paint finish it will start to life off exposing your mill finish and not anodized as speced out, so you could be redoing the whole job again at a loss.
BTW, alodine does require an electric bath to coat aluminum and has the light yellow finish.
 

signbrad

New Member
Regular mill finish aluminum has a oily feel to it

I want to add to Johnny Best's comment about the oily feel of mill finish aluminum.

CLEANING MILL FINISH ALUMINUM

Years ago I worked at a large electric sign company for a while and noticed the painter always washed the raw aluminum before sanding, and then washed it again after sanding and before priming. At the time I questioned his habit of washing twice. He explained that he believed that there were oily deposits on the aluminum when it came from the factory, and that if you sanded without washing first, the deposits could be ground into the aluminum by sanding, causing early paint failure. The second wash, of course, was to remove sanding debris.

Attending the Matthews Painting class since then has confirmed the truth of what this painter claimed. The Matthews instructor said that the manufacturing process does indeed deposit contaminants on the aluminum, and that sanding without an initial solvent wash can embed them into the surface and compromise the adhesion of the primer.
The instructor elaborated that the wiping method was important, too. He said that the wet aluminum should be wiped off before the solvent evaporates, otherwise the contaminants are not being fully removed. He said to look at the wiping cloth and repeat the wash & wipe till it no longer turns black. He also specified wiping in one direction only, not back and forth or round and round. Wiping in one direction actually removes the debris rather than just smearing it around. And he said change cloths frequently to avoid redepositing the contaminants.
To help keep the surface wet while you are wiping it off, the Matthews instructor warned against using a solvent that dried too quickly. He recommended a medium speed solvent that stayed wet till it was removed by the cloth. An example would be Dupont's Final Clean, or Matthews 45330 Speed Prep. Both of these mixes are heavy with VM&P naphtha, which has a medium fast evaporation rate.
I have made my own aluminum cleaner by using our gun cleaning solvent, which is Dupont 105 lacquer thinner, and added VM&P from the paint store to slow it down.

Another trick that is a time saver for quick aluminum cleaning is to apply the cleaning solvent with a three or four-inch brush instead of just misting it on with a spray bottle. I slosh the solvent on liberally with the brush and I'm able to quickly wipe an entire 4x8 sheet before any of it evaporates ahead of my rag. Applying cleaning solvent with a paint brush also helps when you are not cleaning a simple flat surface, such as cleaning brackets or screws, or cleaning a cabinet that has protrusions or reveals.
................

PRIMING ANODIZED ALUMINUM


After I posted the information in my previous post above about the instructions in the Matthews Painting manual about completely renoving an anodized layer before applying paint, I looked at the section again on painting anodized aluminum. Matthews does not recommend using an acid wash primer (like their PT Filler) after removing the anodized finish. They only recommend epoxy primer. No explanation is given, but this will be my next question for our Matthews rep.

Brad in Kansas City
 
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