compare black anodize vs ecoat for cost and weather resistance

[ADM81]

Hi,

We make products that use a frame made of 6061 aluminum extrusions that will exposed to the elements for at least 30 years (the product is guaranteed for 25). The frames are protected using clear anodizing.

Our customers want now want black frames. Any suggestions on the use of black anodizing vs ecoat? Cost is the overriding concern, since we use millions of feet per year of extrusion.

Thanks everyone

ADM

 

[CoryPad]

It will be very difficult to get a black pigmented polymeric coating to maintain adhesion and color for 30 years.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ADM81]

Cory

Thanks for the reply - you make a good point. Our supplier is suggesting something called a "carbon fluorine" coating. Are you familiar with that? Is is still a polymeric coating?

Thanks again for your help.

Dave

 

[IRstuff]

Much of the life expectancy is dependent on usage conditions. Kynar:

http://en.wikipedia.org/wiki/Kynar

is often used as a exterior coating for aluminum roofing and siding, as well as for general exterior painting. The claim is they'll last 50 yrs. That's unclear, but there are plenty of aluminum roofs that show little or no degradation after 15-20 yrs. Kynar is a fluoropolymer, so it might be the cited material.

TTFN

FAQ731-376

 

[TVP]

You need to have your supplier clarify what type of "carbon fluorine" coating they are proposing. Kynar is a thermoplastic fluoropolymer (the correct term), which is one possibility. Another possibility is a resin-bonded coating (PTFE dispersed in an organic layer, typically epoxy) such as the Xylan series from Whitford. Epoxies have terrible UV resistance, so I doubt that this is what they are proposing, but you need to clarify. Either way, this is considerably different from ecoat, which usually means cathodic epoxy electrocoat. Ecoat can also be applied anodically, and there are different formulations based on acrylic not epoxy. Personally I doubt that ecoat on Al will be the desired solution-- probably PVDF or black anodize will be better.

 

[ADM81]

Folks,

Your tips and suggestions have been very helpful.

I think the supplier was talking about a Kynar PVDF coating. I did some more research, and it turns out that our requirements are very similar to that of architectural fenestration requirements (exposures, lifetimes etc). It seems that both black anodizing (E6-C35/BS) and Kynar 500 are good products. So I think it will come down to which one costs less.

Any other thoughts?

Thanks again,

Dave

 

[sreid]

Black anodize is simply dyed anodize (you can get practically ant color you want). Get the aluminum hard anodized (Type III, typically 0.001 to 0.003 thick) and have them dyed black. I believe the black dye also seals the anodize. Check that the finish is cosmetically OK with your customer.

 

[KENAT]

Just to double check, by black anodize do you just mean regular anodize with the black die or do you mean 'hard anodize'.

For some reason when I started here the 2 terms were used interchangeably. This meant lots of parts with relatively expensive anodize when regular anodize with black die would have been fine.

KENAT, probably the least qualified checker you'll ever meet...

 

[ADM81]

Well,

Interesting you should ask. Seems that both the Aluminum Association and AAMA (American Architectural Manufacturers Association) specify a "class 1" anodizing for exerio architectural use. Class 1 can either be Type II OR Type III, but only Type III is hard-coat. Most architectural anodizing is type II and therefor not hard-coat. The AAMA spec is 611. The AA spec is AA-M10C22A44.

Thats a summary of what I have found. Hope it was helpful.

Thanks

Dave