Painted Aluminum Failures in South Florida Exposure

From JPCL, October 2016

By Kirk R. Shields, Corrosion Probe Inc.

Painted aluminum exterior units are rapidly failing in South Florida — sometimes even before the new homes and condos are occupied. This article explores why many painted aluminum practices just don’t work in South Florida, and recommends solutions for building owners and specifiers....


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Tagged categories: AAMA 2603; AAMA 2604; AAMA 2605; Aluminum; Coating failure; Coating inspection; Extrusions; Good Technical Practice; PVDF; Weathering

Comment from BOB HEIDERSBACH, (10/7/2016, 8:19 AM)

Interesting article. Do you have something similar about surface preparation and coating for existing aluminum railings? After Matthew that will be very useful.


Comment from Dick Piper, (10/9/2016, 10:40 AM)

What mil thickness do you recommend for south Florida?


Comment from Kirk Shields, (10/10/2016, 11:38 AM)

As for coating afterwards or on existing railings; if the original or existing system is a baked-on finish like a Kynar, then the available options are 1. Remove, strip/blast and recoat in kind, if your looking for the same longevity and performance provided by the Kynar for gloss and color retention. 2. I've had railings re coated though electrostatic spray methods if the railings could not or would not be removed. So much depends on the locations willingness to explore options that include railing removal with temporary barriers in-place for safety or even closing those balcony's effected from use while work progresses.


Comment from Kirk Shields, (10/10/2016, 11:40 AM)

The thickness is soley up to the coating supplier. The Kynar systems are typically less than 2.0 mils, generally around 1.2 mils or so.


Comment from Aaron Erickson, (10/10/2016, 3:07 PM)

Do you have any thoughts on relative durability of Class I anodized aluminum ( > 0.7 mils) as compared to AAMA 2605 Kynar finishes in the South Florida Exposure?


Comment from Kirk Shields, (10/11/2016, 8:16 AM)

I haven't had allot of experience nor seen anodized much in S. Florida. I would expect the anodized to hold-up much better during the fabrication process as well as incidental contact afterwards, though I'm not sure how long it would hold up along the seacoast versus a Kynar finish.


Comment from Stephen Burdick, (10/11/2016, 9:35 AM)

The real trick is to not have exposed aluminum. Any breach in the coating, edges and seams, will be a open door for filiform corrosion, crevice corrosion and blistering.


Comment from Vincent Casmirri, (10/11/2016, 10:19 AM)

Just a few clarifications about Kynar 500® resin-based coatings. While a Kynar 500® resin-based powder coating is now available, historically they are primarily liquid applied and baked on coatings. Also, for field restoration, coatings exist that are water-based Kynar® finishes meeting AAMA-2605 standards.


Comment from Jesse Melton, (10/12/2016, 7:43 AM)

It all sounds to me like a failure to adopt/adapt thin(ish) film coating technologies from other fields. With a 7x variance in coating thickness on a single part and excess thickness being a lead cause of coating failure it's clear the application process is simply broken and the solution is to repeat it some more. If that's going to be the answer then the money is going to be in prep for recoating, not coating application. Aerospace, pharmaceutical processing systems, high speed machining centers and F1 cars are everyday examples of thin(ish) coatings applied to very complex parts. Some with internal passages that nobody will ever even see. I've never seen a complex architectural component. Exterior railings and such certainly don't qualify. The technology to fix this problem exists and has been proven for 30+ years in life critical applications. Somebody just needs to drive to Huntsville and envision balcony railings instead of rocket and missile parts being coated. Some people actually like South Florida, so I encourage them to look around at the range of alternative coating solutions and just take the entire market away from those resistant to change. Then they can live in one of those expensive buildings instead of working on them.


Comment from Stephen Burdick, (10/12/2016, 8:17 AM)

I agree 100% with Mr. Casmirri. Powder coatings are dominant in Europe, but in the USA, about 90% of the architectural extrusion market is liquid PVDF coating. I know Akzo Nobel has a water-based air dry PVDF repair coating called Trinar Aqua.


Comment from VCBud Jenkins, (10/12/2016, 3:06 PM)

Would it help prevent coating failure and aluminum corrosion if the aluminum had zinc rich primer applied first, then the PVDF? This works on steel, I wonder if it works on aluminum.


Comment from robert richter, (12/28/2016, 7:19 AM)

Have the surfaces under the failures been tested for Soluble Salts? Chlorides, Sulfates, or Nitrates could be absorbing moisture.


Comment from Kirk Shields, (1/3/2017, 8:53 AM)

Once the film failed and being on the coast, salts were deposited and found underneath. The railings were not painted in-place but in a shop environment, typically not exposed to salts. Once the salts were deposited at locations of failing coatings, their presence certainly accelerated the process.


Comment from robert richter, (1/3/2017, 11:31 AM)

Just keep in mind, material that is shipped and stored can have salt deposition from road salts and atmospheric salt. A simple quantitative ion specific salt test would alleviate any surface salt contamination questions.


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