Painting aluminum siding

jsheridan

We're talking about aluminum siding.

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Gymschu

Like I said earlier, buy a HIGH quality paint for aluminum. Aluminum does not soak up the paint like wood does. You can afford to upgrade from the Valspar paint. It's not bad stuff, just not as good as SW's SuperPaint or Duration.

mustangmike3789

we use the SW dtm on aluminum hand rails that go on for miles with an expansion joint at about every 50'. the joint will be over an inch wide in the morning, as it gets hot the joint will be less than 1/4". I live in florida where this takes a lot of heat and salt exposure with a few days of freezing each year.

jsheridan

Thanks Mike, those are some impressive numbers. At those rates, you could probably watch the action. OP lives in Texas, so the heat issue will be comparable.

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jsheridan

If your hat is straw, that will help you get regular real fast.
Just teasin. I'm not a mathematician or a coatings specialist. But, I am a thinking man. It's not handling a one time expansion that's the issue. It's the constant back and forth, the cycle of expansion and contraction, that wears on the bond over time. When you bend a piece of painted aluminum, the paint doesn't initially crack, but as you flex it back and forth it cracks, then it hairlines, then it starts to peel. Nobody's arguing that oil paint is perfectly inelastic, I know that it's not. However, you can't argue that latex isn't superior to oil for flexibility, even in the long run. It comes down to what is the better option for a particular surface and environment. I think you should have placed this post in the other current thread by EdG about exterior painting/priming on wood. I did appreciate the numbers though

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Matthewt1970

Good 1

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Latex Primer: Good for Drywall, that's about it.
Behr Paint: The plastic buckets are good, that's about it.

cherry_560sel

OK......acrylic primer it is !!!! I will add the emulsabond to it though. As far the the topcoat goes, I still have not heard any compeling arguments as to why the Valspar Duramax would not be suitable. I realize that you guys all do this for a living and you want the best quality paint because your work must speak for you, I used to work as a graphics designer and have my share of experience with oil paints as well as acrylics (try $60 for a 8 oz tube !!!!..., layed on THICK for a crunchy texture, then calculate coverage on a 5' x 8' canvas...that would just be the base color, then you have to decide how many colors you will blend in and buy each tube....in one word PRICY...lol) but I have looked at the MSDS of both the Duramax and the SW Duration paints and they both seem to be comparable. Both are also comparably priced (maybe one or two dollars difference). I have actually read articles online that clearly do not recommend the SW Duration because it is way to thick for someone that is inexperienced with the finer points of working with paints, it does not provide true one coat coverage on many substrates, and tends to dry way to fast. Since I will not be using a brush for this job I would still like to discuss the different properties of these paints in the context of spraying them on a non-porous surface.

mustangmike3789

although aluminum may be non-porous it will still have a profile for the paint to anchor to. wash primer needs to be applied @ 1mil dft which is pretty much a mist coat. as soon as you see a translucent green color on the surface of the aluminum, you have applied enough product. follow the product data sheets for correct tip sizes and pressure needed for application. most SW commercial stores will have wet film gauges to help monitor your coating thickness as you apply it.

cherry_560sel

....also, why is epoxy primer not a viable alternative in this case ?

Gymschu

Overkill, and a pain in the butt to use.

mustangmike3789

aluminum is a tuff surface to coat due passivation or its ability to provide its own protective barrier in the form of aluminum oxide. anyone that paints or welds aluminum can tell you how quickly this forms and the bonding issues that it will create. some epoxies can be applied direct to aluminum if the surface is prepared correctly. the correct way to prepare for this is to solvent clean the surface, scuff the surface with a scotchbright pad, rinse with clean water and solvent clean again until there is no sign of gray aluminum oxide on your clean rags and coat immediately. most epoxy coatings require the use of an etch primer or the wash primer before coating aluminum. surface preparation must still be done but the need to scuff will not be required. SW macropoxy 646 can be applied over the wash primer but most epoxy should not be used as a top coat in direct sunlight. acrolon 218 can be applied as a finish coat over the macropoxy. these products are high solids, very heavy and a bit pricey too. macropoxy 646 is an amine epoxy which is prone to amine blushing if it is exposed to moisture during application or during initial curing. amine blush is sort of a waxy coating that can form as moisture is introduce during curing and solvent evaporation and it must be removed before applying a top coat. unless you want to stand in your front yard with a surface contact thermometer, sling psychrometer, and psychrometric charts and constanly check dew points and relative humidity, i would suggest the wash primer with the two coats of primer finish. there may be some other products that im not aware of that may be easier and cheaper but surface preparation on aluminum is an absolute must in my book. i have experience with the macropoxy/acrolon over bare steel and zinc rich primers but have never been required to apply it over aluminum. both macropoxy and the acrolon have short pot life, as low as 2 hours depending on your ambient temperatures.

jsheridan

Thanks Mike, that would chase me back to straight up primer/paint. Especially since my sling psychrometer broke last week and you know how hard it is to find a good psychrometer repairman, let alone a sling one.
I thought I stumbled into a thread about tank coatings.

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cherry_560sel

a sling psychrometer consists of two thermometers mounted together with a handle attached on a chain. One thermometer is ordinary. The other has a cloth wick over its bulb and is called a wet-bulb thermometer. If you really needed one, they are simple to put together....just teasing .

Yeah, nevermind about the epoxy primer...lol.