Simple Green and Aluminum

Untreated aluminum has very good corrosion resistance primarily because it forms a thin (but tough) oxide layer that prevents further oxidation. This aluminum oxide layer is mostly impermeable and it adheres aggressively to the parent metal. If damaged mechanically, the aluminum’s oxide layer self repairs!

That oxide layer is stable in the pH range of 4 to 9, so very acid or alkaline products can remove the layer and begin to attack the parent metal with abandon. This is why most inorganic acids and strong alkaline solutions are very corrosive for aluminum.

Simple Green “regular” (9-10 pH) is above the 9 pH mark, so it can cause degradation of the protective layer. This does depends on how long it is left to sit on the aluminum which also is dependant on how well you rinse it off.

Fortunately the corrosion of the oxide layer can be hindered by using silicates in the solution, this is what you find in things like dishwasher detergents and …. Simple Green Extreme Aircraft (10.1 - 11.7 pH). It is those added silicates in it that protect the aluminum, even though it has a higher pH (according to the msds sheets). This is why you should use Extreme Aircraft and not regular Simple Green when cleaning aluminum parts.

The key word in that is hindered …. so +1 for silicates +2 for complete and thorough rinsing, get those nooks and crannies ;)