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  #1  
Old 01-18-2011, 12:10 AM
dhmoose dhmoose is offline
 
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Default Primer-Sherwin Williams P60G2

Does anyone know what a good P60G2 primer coat looks like? I've used the primer on various sections and get a light green coating after spraying it with a 1:2 p60g2 to reducer ratio. This coat looks considerably thicker then what Vans does on their QB kits. Thoughts? Thanks!
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  #2  
Old 01-18-2011, 12:32 AM
dhmoose dhmoose is offline
 
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Default Pics for prior post...

This link to my log might help demonstrate what I have done:

http://www.mykitlog.com/users/displa...=115268&row=47

David
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  #3  
Old 01-18-2011, 06:13 AM
rv9aviator rv9aviator is offline
 
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Van's primer doesn't have the green pigment in it. For some reason it is sold overseas without the green pigment. At least that is what I was told. If your paint is splotchy try using a little more reducer. I ended up using 2 parts reducer or activator to one part primer.
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  #4  
Old 01-19-2011, 01:09 PM
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Bill.Peyton Bill.Peyton is offline
 
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The primer Vans uses is not a corrosion preventative primer and is called a wash primer. The sole purpose of this type of primer is to promote adhesion, and not for corrosion. I am not at home or I would provide you with the part number of the Vans paint. The 2 part primer that I used on top of Vans primer, and for all subsequent un-primed parts is shown on my website www.mykitlog.com/peytonb. Normally you do not need to use a thick coat to promote good adhesion, but because you are probably using it as a corrosion barrier, you should put it on thick. This stuff is really bad for you to breath, so a positive pressure mask is a must!
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  #5  
Old 01-19-2011, 01:24 PM
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JonJay JonJay is offline
 
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Default This is a true statement but it does have protective qualities.

Quote:
Originally Posted by Bill.Peyton View Post
The primer Vans uses is not a corrosion preventative primer and is called a wash primer. The sole purpose of this type of primer is to promote adhesion, and not for corrosion.
There is no coating that "prevents" corrosion, only gradients from no protection to very good protection. Van's "unofficial" testing of the wash primer showed it protected significantly better than unprimed Alclad.
I am told the test was strips hung from the outside staircase for a year at the factory in the elements. The unprimed Alclad showed a lot of surface corrosion. The wash primer showed none. The factory is located in an environment of lots of rain, little or no salt, and pretty low humidity (when it is not raining!, it's Oregon, it rains a lot here!). That test is what they based the decision to use the wash primer on the QB's I am told.

If you read the wash primer manufacturers own data it specifically says it has minimal corrosion protection, or "poor", I believe it stated. It is still far better than nothing even though many thousands of airplanes live and fly today without any protection, and no corrosion.
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  #6  
Old 01-19-2011, 01:27 PM
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JonJay JonJay is offline
 
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Default Dont put it on thick...

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Originally Posted by Bill.Peyton View Post
Normally you do not need to use a thick coat to promote good adhesion, but because you are probably using it as a corrosion barrier, you should put it on thick.
I believe SW specifies 4 mils. It warns that thicker coatings may cause adhesion problems (peeling) with the primer.
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  #7  
Old 01-19-2011, 01:37 PM
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Default I believe it should be 1:5 to 1 ratio

Quote:
Originally Posted by dhmoose View Post
Does anyone know what a good P60G2 primer coat looks like? I've used the primer on various sections and get a light green coating after spraying it with a 1:2 p60g2 to reducer ratio. This coat looks considerably thicker then what Vans does on their QB kits. Thoughts? Thanks!
It states this on the product. From David's kit log, that shows a bit more pigment than what I like to see, although I had many parts look like that and I would not do them over.
The appearance should be a transluscent green without any small dots of green or blotches, in other words a continuous smooth sheen of very light green. That is about the 4 mils recommended by SW. Anything with a mottled appearance usually means that it did not atomize very well out of your gun.
It takes some practice to get the gun set. HVLP's are a bit tricky with this product but you can still get a good result with the right set up. Take practice shots on some scrap until you get that suttle sheen and then blast away.
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  #8  
Old 01-19-2011, 06:03 PM
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Bill.Peyton Bill.Peyton is offline
 
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Jonjay,
In regards to the corrosion protection, one only need to read the data sheet for the wash coating Vans applies. It states, as I recall, it should not be used for corrosion protection. My only point is that Vans could have selected a much better product at very little difference in cost, and saved a lot of us a lot of time.
I really don't care how many production spam cans are out there flying without any protection. My current 25 year old hangered Piper does not have it and I can already see the start of discoloration in the wings which was not there 20 years ago. In 1980 it was a Piper option to have the interior panels treated, unfortunately the guy who owned the aircraft prior to me chose not to pay for the option.

In regards to the RV-10, when I sink almost $200K and 2 years into an airplane, I would like to think that it will have the best solution possible for corrosion protection. Most who are building the slow kits are using the two part epoxy chromates which accomplish this to a much greater extent than a wash primer.
In regards to the thickness of the coating, I understand the data sheet does indeed specify a very thin layer for use of the product as an undercoat layer, but there are a lot of areas that will never get a finish coat that will benefit from a thicker coating. By "thicker" I mean covering the underlying material sufficiently that it appears a consistent green. I personally have not seen any issues of pealing. I would guess if it was put on real thick there could be issues. Like I stated, I have not seen this peeling issue. It seems once this stuff is put on it is extremely durable.
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  #9  
Old 01-20-2011, 08:54 AM
dhmoose dhmoose is offline
 
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Default Thanks!

I appreciate all the replies and comments. My intention was not to start a primer war, but to get opinions on the method to use for SW P60G2. Another way to word the question would be..."What does 4 mils of SW P60G2 look like?" In my experience (empennage), I have strayed from the manufacturer recommended 1:1.5 and used 1:2. It seems to work well but as was mentioned, this material is difficult to shoot with an HVLP gun. Avoiding runs (it has a consistency like water) and blotches takes patience but with a couple coats, the result seem good. I get a full surface coat with no "untouched" areas. I have not seen any peeling, even when I have scuffed an area accidentally when riveting. So, I'm confident that the coverage is good and will last. What I can't be sure of is the "corrosion protection" of it and the ideal thickness (SW does say that it does not provide corrosion protection in their sheet). Since Vans tested it, speaks favorably about it, and uses it on the QB, I'll assume the corrosion protection is sufficient. So, the only issue is, "What does 4 mils of SW P60G2 look like?" (without a paint thickness tester)
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  #10  
Old 01-20-2011, 09:44 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Default A few points about P60G2 (and protective primer in general)

Quote:
Originally Posted by Bill.Peyton View Post
Jonjay,
In regards to the corrosion protection, one only need to read the data sheet for the wash coating Vans applies. It states, as I recall, it should not be used for corrosion protection. My only point is that Vans could have selected a much better product at very little difference in cost, and saved a lot of us a lot of time.
I really don't care how many production spam cans are out there flying without any protection. My current 25 year old hangered Piper does not have it and I can already see the start of discoloration in the wings which was not there 20 years ago. In 1980 it was a Piper option to have the interior panels treated, unfortunately the guy who owned the aircraft prior to me chose not to pay for the option.

In regards to the RV-10, when I sink almost $200K and 2 years into an airplane, I would like to think that it will have the best solution possible for corrosion protection. Most who are building the slow kits are using the two part epoxy chromates which accomplish this to a much greater extent than a wash primer.
In regards to the thickness of the coating, I understand the data sheet does indeed specify a very thin layer for use of the product as an undercoat layer, but there are a lot of areas that will never get a finish coat that will benefit from a thicker coating. By "thicker" I mean covering the underlying material sufficiently that it appears a consistent green. I personally have not seen any issues of pealing. I would guess if it was put on real thick there could be issues. Like I stated, I have not seen this peeling issue. It seems once this stuff is put on it is extremely durable.
It is correct, that Sherwin Williams does not promote P60G2 as a corrosion protective coating on aluminum.
This is also true of a large # of the other coatings that RV builders choose to use. Most manufacturers require the coating to be paint top coated for true protection.
P60G2 has Chromates in it. This is a common ingredient of protective primers (like the popular Tempo brand Zinc Chromate primer). The chromates act as a sacrificial anode to the development of corrosion.

As mentioned by Jonjay...Vans has an outdoor exposure test sample that has been outside in the Oregon weather, but under cover so it has no U.V. exposure. It has been in place since April, 2002, so it has been in place almost 9 years. A recent inspection showed that the bare alclad surface under the P60G2 coat has zero indication of corrosion. The bare, uncoated portion of the test sample has corrosion.

My experience using P60G2 for the past 20 years is that there can be variation from one can to another. Often it is unsprayable if mixed to the recommended 1.5:1 ratio. I usually mix at 2:1 (but not always...depends on the consistancy of that particular can).
Most beginners tend to spray it too heavy. When properly mixed, spray just heavy enough to wet the entire surface (resist the temptation to add more regardless of how dark it looks).
The color tends to darken slightly as it dries.
Proper application results in what looks like a very light green anodized coating.
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