gmcjetpilot
Well Known Member
the famous or infamous debates on primers is a a big dead horse I don't want to resurrect, but in the last RVator a home grown test was done and was interesting and matched common sense or at least what I expected.
Tested: Bare Clad, Wash primer on unprepped aluminum
Samples where left out for 3.5 years, 11 months if which was rain in the Oregon weather near the Pacific. The wash showed the alumium was still shinny under the wash primer. The bare showed some corrosion but very slight. The author compared it to what he had seen in the tail cone of certified planes, with unprimed clad aluminium after 15-20 years.
The author's conclusion was the single step wash primer did provide protection that although may be not on par the 3 - 4 step Mil spec process (scotch brite, etch, alodine, prime) it did well. It also showed that for a light economy solution no prime was a reasonable approach since the corrosion was negligible. The conclusion was the wash primer does add some extra value to the plane and their (Van's) process used on the QB's was value added, and provides an option that is not as expensive and labor intensive as the Mil spec multi process primer, which builder should consider. So the conclusion is no conclusion. It is a personal choice. At least that is what I got out of it.
Please write Van's if you disagree (after your read the whole article); I am only providing the info. (My opinion/theory is to prime the unclad parts that are significant structure or hard to inspect due to stack up with the good multi process stuff, and leave the rest unprimed to save cost and weight. I think the airframe will last a life time, or at least my lifetime, while keeping weight, build time and cost down.) George
PS: There was also a great idea on aligning gear leg fairings in the same Dec issue of the RVator. If you don't have a subscription I think it is worth it.
Tested: Bare Clad, Wash primer on unprepped aluminum
Samples where left out for 3.5 years, 11 months if which was rain in the Oregon weather near the Pacific. The wash showed the alumium was still shinny under the wash primer. The bare showed some corrosion but very slight. The author compared it to what he had seen in the tail cone of certified planes, with unprimed clad aluminium after 15-20 years.
The author's conclusion was the single step wash primer did provide protection that although may be not on par the 3 - 4 step Mil spec process (scotch brite, etch, alodine, prime) it did well. It also showed that for a light economy solution no prime was a reasonable approach since the corrosion was negligible. The conclusion was the wash primer does add some extra value to the plane and their (Van's) process used on the QB's was value added, and provides an option that is not as expensive and labor intensive as the Mil spec multi process primer, which builder should consider. So the conclusion is no conclusion. It is a personal choice. At least that is what I got out of it.
Please write Van's if you disagree (after your read the whole article); I am only providing the info. (My opinion/theory is to prime the unclad parts that are significant structure or hard to inspect due to stack up with the good multi process stuff, and leave the rest unprimed to save cost and weight. I think the airframe will last a life time, or at least my lifetime, while keeping weight, build time and cost down.) George
PS: There was also a great idea on aligning gear leg fairings in the same Dec issue of the RVator. If you don't have a subscription I think it is worth it.
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