Corrosive to Aluminum
The aviation industry avoids using Simple Green on airplanes because of documented corrosion of Simple Green to aluminum parts. Airplanes can have a useful lifetime of 30 to 60 years and corrosion is taken very seriously to extend the lifetime of the aircraft.
AvWeb News Article (Dated: May 18, 2000)
A well-known aviation magazine this month published a feature article on cleaning one's aircraft and getting it ready for spring flying. Only one problem -- a product the article recommended as safe for aviation use has been proven corrosive to aluminum. The product is Simple Green, a popular household cleaning liquid. According to the magazine's May issue -- which included a photo of Simple Green and other products -- the liquid "does an admirable job for a fraction of the cost of the aviation cleaners." While that may be true as far as it goes, both the U.S. Air Force and the U.S. Army have conducted tests of Simple Green and strongly urge that it not be used to clean aluminum structures. In one test conducted by the U.S. Air Force, results from which were published in 1989, aluminum alloy samples were immersed in Simple Green for a week then removed, cleaned and weighed. The results indicated that the approximately 3.5-gram aluminum alloy samples experienced a material loss of about 31 milligrams in a diluted solution and a whopping 295 milligram loss after spending a week in the undiluted liquid. The Air Force report summed it up this way: "We do not recommend the use of this product on Air Force equipment containing aluminum." Good advice, that.
USAF Testing Report: http://www.avweb.com/other/usaf0020b1.pdf
The aluminum samples were tested for weight loss (i.e. corrosion) and also for appearance according to the scale below
0 = No visible corrosion
1 = Very slight corrosion or discoloration
2 = Slight corrosion
3 = Moderate corrosion
4 = Extensive corrosion and pitting
All of the samples were evaluated as a 3 or 4 on the rating scale.
As stated above in the AvWeb article, there was significant weight loss (1% and 8% in 7 days for the dilute and concentrated tests).
Here is a statement from Simple Green's Website: http://www.simplegreen.com/faq.html
Aluminum - Is it safe to use Simple Green on aluminum?
Simple Green products have been successfully and safely used on aircraft, automotive, industrial and consumer aluminum items for over 20 years. However, caution and common sense must be used: Aluminum is a soft metal that easily corrodes with unprotected exposure to water. The aqueous-base and alkalinity of Simple Green or Crystal Simple Green can accelerate the corrosion process. Therefore, contact times of All Purpose Simple Green and Crystal Simple Green with unprotected or unpainted aluminum surfaces should be kept as brief as the job will allow - never for more than 10 minutes
. Large cleaning jobs should be conducted in smaller-area stages to achieve lower contact time. Rinsing after cleaning should always be extremely thorough
- paying special attention to flush out cracks and crevices to remove all Simple Green/Crystal Simple Green residues. Unfinished, uncoated or unpainted aluminum cleaned with Simple Green products should receive some sort of protectant after cleaning to prevent oxidation. (Bolding is my emphasis
I don't know the exact composition of the alloy wheels and whether they will resist the corrosive properties of Simple Green. If you want to use it, sounds like brief exposure with extensive rinsing is recommended.
(Happy flying, er... I mean Piloting)