Since it has been a while since any info about this test has been provided, I thought it was time for an update.
As has been mentioned in the past, this test is about as un-controled as any can get and it in no way am I meaning to imply that it compares to any of the Mil Spec lab executed tests that are commonly done to test the performance of protective coatings, but I feel it still provides some worthwhile real world situations data that can be used when making the prime / don't prime / what primer should I use, decision.
Though Sherwin Williams doesn't officially endorse P60G2 as a protective coating unless it is top coated, I think the results of this unscientific test show that it does provide a good level of protection which makes it a good choice when factored against cost, added weight, and ease of application, which is why we have used it for decades in our shop at Van's, on the production QB kits, and recommended it in our construction manual as one potentially good option.
The test -
On April 15, 2002, I made a test panel of .020 thick 2024-T3 aluminum. The panel was divided vertically into thirds with the right side third having nothing done to it.
The center third was cleaned with a wax/grease remover and the left side third was scuffed with grey Scotchbrite and then cleaned with wax/grease remover.
The left and center third was then sprayed with P60G2 mixed 2:1 - reducer : primer.
The test panel was then hung outside, but underneath an outdoor stairway so that it is not exposed to direct sunlight, etc.
For reference, we are in a rather humid/wet environment (for part of the year anyway) and the pacific ocean is about 60 mile direct west of here.
The test panel was left for about 4 years and then a 1/2" wide strip was exposed along the top by removing the primer. The surface was like brand new under where the primer was, but the right side third that was not primed had shown a very slight indication of surface corrosion.
Fast fwd 4 more years to Sept 2010. Exposed another 1/2 wide area and found same results.
Fast fwd 4 more years to Sept 2016. Exposed another 1/2 wide area ( skipped a row for better definition) and found same results.
Fast fwd to the current date and exposed another row in Oct 2020. Found same result. It may look a little splotchy in the photo but that is only because I didn't work to get every single bit of the primer off (as it has aged, removal of the primer with solvent seems to be getting more and more difficult)
As each row has been exposed, from that point on it has begun to develop some detectable level of surface corrosion and the nearly 19 years that the unprimed right side third has been exposed it definitely shows signs of corrosion but still not to a degree that would make an aircraft un-airworthy if found on interior skins.
All in all I think this shows that for a low cost, low weight gain, and easy to apply primer, it does offer some valuable corrosion protect and it will continue to be the go to choice here at Van's.
As has been mentioned in the past, this test is about as un-controled as any can get and it in no way am I meaning to imply that it compares to any of the Mil Spec lab executed tests that are commonly done to test the performance of protective coatings, but I feel it still provides some worthwhile real world situations data that can be used when making the prime / don't prime / what primer should I use, decision.
Though Sherwin Williams doesn't officially endorse P60G2 as a protective coating unless it is top coated, I think the results of this unscientific test show that it does provide a good level of protection which makes it a good choice when factored against cost, added weight, and ease of application, which is why we have used it for decades in our shop at Van's, on the production QB kits, and recommended it in our construction manual as one potentially good option.
The test -
On April 15, 2002, I made a test panel of .020 thick 2024-T3 aluminum. The panel was divided vertically into thirds with the right side third having nothing done to it.
The center third was cleaned with a wax/grease remover and the left side third was scuffed with grey Scotchbrite and then cleaned with wax/grease remover.
The left and center third was then sprayed with P60G2 mixed 2:1 - reducer : primer.
The test panel was then hung outside, but underneath an outdoor stairway so that it is not exposed to direct sunlight, etc.
For reference, we are in a rather humid/wet environment (for part of the year anyway) and the pacific ocean is about 60 mile direct west of here.
The test panel was left for about 4 years and then a 1/2" wide strip was exposed along the top by removing the primer. The surface was like brand new under where the primer was, but the right side third that was not primed had shown a very slight indication of surface corrosion.
Fast fwd 4 more years to Sept 2010. Exposed another 1/2 wide area and found same results.
Fast fwd 4 more years to Sept 2016. Exposed another 1/2 wide area ( skipped a row for better definition) and found same results.
Fast fwd to the current date and exposed another row in Oct 2020. Found same result. It may look a little splotchy in the photo but that is only because I didn't work to get every single bit of the primer off (as it has aged, removal of the primer with solvent seems to be getting more and more difficult)
As each row has been exposed, from that point on it has begun to develop some detectable level of surface corrosion and the nearly 19 years that the unprimed right side third has been exposed it definitely shows signs of corrosion but still not to a degree that would make an aircraft un-airworthy if found on interior skins.
All in all I think this shows that for a low cost, low weight gain, and easy to apply primer, it does offer some valuable corrosion protect and it will continue to be the go to choice here at Van's.
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