Question Aluminum Finishes And Durability Concerns

[Caliber Sign Guy]

We've used brushed (and polished) raw aluminum in interior signs for years, as well as some of the "stock" anodized aluminum finishes as well. We've used them in exterior settings as well...I've always wondered how necessary/recommended it was to use a clear coat to protect/prolong these kinds of finishes in exterior settings though we always have cleared our raw aluminum. This actually caused an issue once... (it's been years ago, but a whole set of letters like this started to yellow and peel and basically had to be stripped and redone - this time with powder coated clear protective finish) and it makes me wonder, given the relatively mild/subtle impact of oxidation on aluminum, is it even necessary to do so? And with the anodized stock finishes like this offered on aluminum - how outdoor durable are these? Any general feedback/advice/observations by all the experienced sign folks on this forum would be much appreciated!

 

[printhog]

Depends on the environment the signs are in. Near salt air I'd say a clear coat would be advisable. In the Las Vegas desert, much less need. Aluminum oxidizes with water contact. So if landscaping sprinklers, road salt spray or snow can deposit on it, then clear coat.

You have to ask yourself if your making a monument to last generations or a sign (by monument I don't mean shopping center monument style, I mean national park kind of thing). If your a monument kind of shop, then your prices should reflect the extra treatments for longevity.

But if it's just a sign, in practice it'll likely be replaced within 20 years. Fashion trends change, so do business logos.

The trend in business graphics is a full rework of identity in 7 year cycles. I'd aim for the product that gets that life. Bare aluminum will with some exceptions.

As for clear yellowing, some urethanes years back did that. The manufacturers have since improved the products.

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[Johnny Best]

Anodized Aluminum holds up very well outside, but mill finish aluminum has to have a good two part clear coat to protect it, if not it will start to show oxidation fairly quickly in harsh environments. Mill finish has to be prepared right before clears are applied to get the protection needed

 

[Jean Shimp]

We have a set of letters with Chemmetal brushed aluminum laminated to PVC that we installed in 2003. The letters are on a south facing wall, which is brutal exposure in the Florida sun. If you look closely you can see small pitted areas in the surface. Personally I would have replaced the letters but the owner is fine with them.

 

[Johnny Best]

This is on Chemetal webpage:
Is Chemetal okay for outdoor use?

No, Chemetall is for indoor applications only. Our coatings and our anodized aluminums are rated for interior use.

 

[equippaint]

Does anodizing help with uv exposure and/or oxidation, i understand the process but not the purpose.
Has anyone had issues with 2k clears peeling on aluminum? Aluminum is usually pretty rough to get topcoats to stick to if you dont etch and alodine or wash prime but thats obviously not possible here.

 

[Johnny Best]

If you clean the aluminum, give it a sanding till all the oxide is gone, solvent clean use a wash primer and two part clear coat it should hold up pretty well.
Anodized alum is better than mill finish as far as holding up better, but it will still see the effects of oxidation as to where it is located (salt, weather).
Back in the 70s we use a lot of gold anodized alum for cabinets and I still see some of those still up and not that bad looking, they have wear and fade but thats to be expected after a long time with any material.

 

[Caliber Sign Guy]

Depends on the environment the signs are in. Near salt air I'd say a clear coat would be advisable. In the Las Vegas desert, much less need. Aluminum oxidizes with water contact. So if landscaping sprinklers, road salt spray or snow can deposit on it, then clear coat.

You have to ask yourself if your making a monument to last generations or a sign (by monument I don't mean shopping center monument style, I mean national park kind of thing). If your a monument kind of shop, then your prices should reflect the extra treatments for longevity.

But if it's just a sign, in practice it'll likely be replaced within 20 years. Fashion trends change, so do business logos.

The trend in business graphics is a full rework of identity in 7 year cycles. I'd aim for the product that gets that life. Bare aluminum will with some exceptions.

As for clear yellowing, some urethanes years back did that. The manufacturers have since improved the products.

Sent from my SM-G900T using Tapatalk

That's about what I've been thinking. We've probably over-engineered some of these over the years - but we did charge appropriately and they have all lasted nicely with the exception of the one we fixed which I mentioned...thanks for the input!