# Painting aluminum siding



## cherry_560sel (Dec 6, 2010)

Sometime this summer I will be painting the exterior of my home. The house is covered with aluminum siding. The paint is chalked and there are bare spots where there is only a minimal residue of old chalky paint covering the area. In short, the siding needs a new coat of paint really really bad. So here's my plan: Take the time to clean the aluminum siding properly (brush, TSP, and lots of hard work), fill small dents with metal filler (bondo), use an oil based primer, followed by a 100% acrylic latex paint. My concern is that after reading many post I have begun to doubt my choice of using the Valspar brand of paint. I plan on using an airless sprayer for the job. My main question is, given that I will be using a primer tinted 50% to the final color, will using Valspar give me good results considering the medium it will be applied to? The siding has a "faux wood grain" and looks like it can go for at least ten more years. BTW, I have peaked underneath the aluminum siding and the clapboards underneath look like they are in awesome shape given that they were last painted over 60 years ago. :laughing:


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## jsheridan (Jan 30, 2011)

Sounds ambitious, also sounds like you have a good handle on it. My only question is why the oil primer? My concern is the temp fluctuations and the fact that oil won't flex that well on metal under hot Texas sun and cool nights. Personally, I would spot prime any exposed aluminum and two coat with finish. I would go with a Ben Moore system, they have a latex primer that will handle the exposed aluminum and their Moor line of exterior paint has excellent adhesion qualities. The Moor products will grab on to that with a death grip, and with spray the siding will look factory finished. I'm sure the other top manufacturers have comparable systems but my experience is with BM, and I wouldn't recommend anything but the top line products on exteriors. If you can carry the extra cost, the results and peace of mind will be worth it.


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## poppameth (Oct 2, 2008)

1) Aluminum does not like oil. After you prep prime with a 100% acrylic primer like Zinsser 1-2-3. If you still have any chalking issues, use Zinsser Peelstop instead to bind any residue.
2) Use a higher quality paint. Nothing in the big box stores is all that great. Ben Moore, Sherwin Williams, Pratt and Lambert, etc. will all have better products at a comparable price.


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## housepaintingny (Jul 25, 2009)

You do not need oil base primer. I would use a latex base primer and you only need to prime the areas that have raw aluminum. I prefer to use SW DTM Bonding Primer and SW SuperPaint, saitn when painting aluminum siding. You will need to apply 2 coats of a quality 100% acrylic latex paint. Sounds like you have a handle on the cleaning aspect of the siding.


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## Gymschu (Dec 12, 2010)

housepaintingny said:


> You do not need oil base primer. I would use a latex base primer and you only need to prime the areas that have raw aluminum. I prefer to use SW DTM Bonding Primer and SW SuperPaint, saitn when painting aluminum siding. You will need to apply 2 coats of a quality 100% acrylic latex paint. Sounds like you have a handle on the cleaning aspect of the siding.


Great advice as always! A side note: You don't use a whole lot of paint on aluminum siding............so splurge a little and put something good on it like the above mentioned SuperPaint. There are some aluminum sided houses I painted 15 years ago that look almost as good as the day it was put on.


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## cherry_560sel (Dec 6, 2010)

jsheridan said:


> Sounds ambitious, also sounds like you have a good handle on it. My only question is why the oil primer? My concern is the temp fluctuations and the fact that oil won't flex that well on metal under hot Texas sun and cool nights. Personally, I would spot prime any exposed aluminum and two coat with finish. I would go with a Ben Moore system, they have a latex primer that will handle the exposed aluminum and their Moor line of exterior paint has excellent adhesion qualities. The Moor products will grab on to that with a death grip, and with spray the siding will look factory finished. I'm sure the other top manufacturers have comparable systems but my experience is with BM, and I wouldn't recommend anything but the top line products on exteriors. If you can carry the extra cost, the results and peace of mind will be worth it.


Well, from all the research I have done for this project, I keep reading over and over that the primer should be an oil based product due to the fact that an oil based primer will adhere better to the chalky finish. I scrubbed a small area on the corner of the house to see exactly how the cleaning aspect will proceed and after it dried I could still rub off paint with my hand. Also, I have read that an oil based primer does not contain the amonia that the latex primers do. Supposedly, over time, this will react with the aluminum causing it to oxidize and creates air bubbles that rise underneath the latex top coat. I just don't want to take the chance of that happenening. The siding is far past the point of being able to spot prime. What I am most concerned about is the paint that I will be using as topcoat. Like you say, you have experience with BM paints. What exactly is the difference when it comes to all the different brands. They all seem to cost about the same per 5 gallon buckets and from reading the specs they seem to be comparable, but I have been reading on this forum alot about staying away from Behr or Valspar paints and I would like to know what makes them so bad compared to the other brands.


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## housepaintingny (Jul 25, 2009)

cherry_560sel said:


> Well, from all the research I have done for this project, I keep reading over and over that the primer should be an oil based product due to the fact that an oil based primer will adhere better to the chalky finish. I scrubbed a small area on the corner of the house to see exactly how the cleaning aspect will proceed and after it dried I could still rub off paint with my hand. Also, I have read that an oil based primer does not contain the amonia that the latex primers do. Supposedly, over time, this will react with the aluminum causing it to oxidize and creates air bubbles that rise underneath the latex top coat. I just don't want to take the chance of that happenening. The siding is far past the point of being able to spot prime. What I am most concerned about is the paint that I will be using as topcoat. Like you say, you have experience with BM paints. What exactly is the difference when it comes to all the different brands. They all seem to cost about the same per 5 gallon buckets and from reading the specs they seem to be comparable, but I have been reading on this forum alot about staying away from Behr or Valspar paints and I would like to know what makes them so bad compared to the other brands.



The chalkyness, which is from oxidation of the aluminum breaking down should all be washed off prior to painting. You will only have to prime any bare aluminum and use a quality latex bonding primer. Then apply a quality acrylic latex paint. Aluminum siding expands and contracts a lot and also conducts heat an acrylic latex can resist heat more and also expand and contract, where a oil base won't.


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## Gymschu (Dec 12, 2010)

Cherry, been doing this painting thing for over 30 years. Tried the oil-base primer for aluminum ONCE. Pain in the butt to use, dried poorly on the aluminum, and left me with a less than desirable base coat for my topcoats. Have used latex primer on bare aluminum and topcoated with SuperPaint on many aluminum sided homes. Have never, ever had a problem with peeling or bubbling paint. The only issue I see is that some colors fade after 7 or 8 years.


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## mustangmike3789 (Apr 10, 2011)

i would use Sherwin Williams DTM wash primer with two coats of of DTM primer/finish. this system is extremely durable and covers very well. the wash primer only needs to be applied at .7 mils dry film thickness, so it will cover over 300 sqft per gallon. we use this coating over aluminum and galvanized steel in corrosive marine enviroments with no failures. it may be close to the BM product mentioned earlier.


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## jsheridan (Jan 30, 2011)

Cherry, if you're concerned about residual chalkiness after washing, you can get some Emulsa Bond, which helps latex bond to chalky surfaces. Without getting too technical, higher quality paints use higher quality raw materials. Cheaper eggshells have less sheen because they use lower grade resins, higher grade paints use titanium dioxide as pigment to hide while lower grade paints use basically chalk and clay, etc. The list goes on and on through color retention, sheen retention, durability, etc. You do get what you pay for when you purchase premium paints. How hot do you think that aluminum siding gets when the air temp in Texas is over 100 degrees, probably close to 150 (I'm not a scientist, but I've gotten burned on siding once or twice) Then, what's it go down to at night. Aluminum siding is very thin and that's a lot of expansion and contraction, in my opinion, for an oil to handle. The oil will bond to the surface, but the stress will break that bond. I don't know about the ammonia issue you mentioned. SW makes a primer specifically for non ferrrous metal, aluminum included, so I'm sure that if an ammonia reaction was possible they'd have learned that and adjusted the formula. You've got probably 100+ years experience advising you on this thread to not use oil. We're here to help you get your job done properly, trust us. 
Here is a link to mustangmike's reference http://protective.sherwin-williams.com/detail.jsp?A=sku-26000%3Aproduct-6787


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## Matthewt1970 (Sep 16, 2008)

jsheridan said:


> Cherry, if you're concerned about residual chalkiness after washing, you can get some Emulsa Bond, which helps latex bond to chalky surfaces.


Yes. Use Emulsa Bond. Wash off as much of the chalk as you can but nothing will get it 100%.


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## cherry_560sel (Dec 6, 2010)

Matthewt1970 said:


> Yes. Use Emulsa Bond. Wash off as much of the chalk as you can but nothing will get it 100%.


 
:laughing:,,,ok, and your signature says ...Latex primer, good for drywall. that's about it......sorta gives me pause. So what is the opinion of Valspar duramax acrylic paint? has anyone here used it before?


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## Matthewt1970 (Sep 16, 2008)

cherry_560sel said:


> :laughing:,,,ok, and your signature says ...Latex primer, good for drywall. that's about it......sorta gives me pause. So what is the opinion of Valspar duramax acrylic paint? has anyone here used it before?


Valspar is better than Behr but not much. Get some real paint from a real paint store. Pittsburg, Benjamin Moore, Sherwin Williams are my top choices. If you do happen to have some bare alluminum then a bonding latex primer would be ok. I am at odds with housepaintingny about oil not expanding and contracting and heat, we have been using oil based paint for over 100 years and it has been expanding and contracting all along. Other than that he is spot on with his advice.


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## jsheridan (Jan 30, 2011)

cherry_560sel said:


> :laughing:,,,ok, and your signature says ...Latex primer, good for drywall. that's about it......sorta gives me pause. So what is the opinion of Valspar duramax acrylic paint? has anyone here used it before?


Half the battle has been won, he's at least considering latex primer:laughing:. Don't listen to Matt's sig. IMO, latex primers are far superior to oil in some respects, and I'm partial to oil. It's especially true with the characteristics you need, flexibility and bonding. I'm not familiar with your choice, so can't comment. I would suggest seriously considering Mustang Mike's rec of SW DTM (Direct to Metal) wash primer. The man is a certified coatings/corrosion inspector, so I'll take his word on it. It may be a little pricey, but the entire success of the job rests on the primer. My only question for Mike would be 
Will it bond and stay bonded with expansion and contraction of siding?
Will it be flexible enough? Kind of related questions.


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## Matthewt1970 (Sep 16, 2008)

Just consider this. If you have a 12' bord, which is about the longest you will find on a home, here is your Coefficients of Expansion for wood.
0.0000027 Coefficient of Expansion in inches of expansion per inch of material per degree F. Lets take 100 degree swing.

0.0000027 x 100 Degrees = 0.00027 inches of expansion per inch of material
0.00027 x 144" = 0.0388 inches per 12 feet of board. 

If oil based paint can't handle .0388 inches of expansion in 12 feet of wood then I will eat my whole hat.


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## jsheridan (Jan 30, 2011)

We're talking about aluminum siding.


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## Gymschu (Dec 12, 2010)

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.


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## mustangmike3789 (Apr 10, 2011)

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.


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## jsheridan (Jan 30, 2011)

mustangmike3789 said:


> 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.


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 (Jan 30, 2011)

Matthewt1970 said:


> Just consider this. If you have a 12' bord, which is about the longest you will find on a home, here is your Coefficients of Expansion for wood.
> 0.0000027 Coefficient of Expansion in inches of expansion per inch of material per degree F. Lets take 100 degree swing.
> 
> 0.0000027 x 100 Degrees = 0.00027 inches of expansion per inch of material
> ...


If your hat is straw, that will help you get regular real fast. :laughing:
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:thumbsup:


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## Matthewt1970 (Sep 16, 2008)

jsheridan said:


> If your hat is straw, that will help you get regular real fast. :laughing:


Good 1


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## cherry_560sel (Dec 6, 2010)

:jester:

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.


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## mustangmike3789 (Apr 10, 2011)

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.


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## cherry_560sel (Dec 6, 2010)

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


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## Gymschu (Dec 12, 2010)

cherry_560sel said:


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


Overkill, and a pain in the butt to use.


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## mustangmike3789 (Apr 10, 2011)

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.


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## jsheridan (Jan 30, 2011)

mustangmike3789 said:


> 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.


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.:laughing:
I thought I stumbled into a thread about tank coatings.


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## cherry_560sel (Dec 6, 2010)

jsheridan said:


> 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.:laughing:
> I thought I stumbled into a thread about tank coatings.


:whistling2: 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 :yes:.

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


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