Simple Green and Aluminum Embrittlement

tom p.

tom p.

Active member
I've had long-term concerns about Simple Green due to some negative experiences with it. I know some people love the product and say there's no issue or concerns with it using it on the cars we love.



I suspect this will be controversial but here's some information I came across from the DoD:



Simple Green and other cleaners that are not listed in the Technical Manuals are taboo for a very good reason - they hurt the metal used to build the machine.







It has been brought to the attention of the U.S. Army Aviation Missile Command (AMCOM) Depot Maintenance Engineering Team that numerous units are using the commercial product SIMPLE GREEN as an aircraft wash. STOP! This product has been through Department of Defense (DOD) testing and was determined to be highly corrosive on aircraft aluminum and also a catalyst for Hydrogen Embrittlement in high strength aircraft alloys.





Hydrogen Embrittlement brought down Chinook 89-00173 on 10 October 1992, near Fort Richardson, Alaska.



While a highly effective cleaning agent for floors and non-aluminum / non-high strength alloy vehicles this product is not approved for aviation usage. If your unit has been using SIMPLE GREEN on a regular basis, it is recommended that a thorough fresh water wash with the approved cleaners per the appropriate airframe maintenance manuals be accomplished as soon as practicable. This should be followed up with a corrosion inspection / treatment and application of approved Corrosion Prevention Compounds (CPCs).
Click to expand...





links: http://www.chinook-helicopter.com/maintenance/issues/cleaners/cleaners.html and https://safety.army.mil/pages/media/pubs/ff/ffmar2000.doc (.doc)





(thread title edited for technical accuracy)
 
I've been hearing a good deal about this lately, and recetly I've had a couple of mixed outcomes on GM machined/cleared wheels.



I think I might look towards Auto Magic's Triple 7 APC.
 
I've always been a fan of Simple Green - but there is no doubt that it is strong stuff. I wonder if they were using it a full strength. I always dilute it quite heavily and rinse very thoroughly. Makes you wonder though . . . :hm
 
Your title is a bit misleading, as hydrogen embrittlement occurs in steels. Your quote refers to corrosion of aircraft aluminum and hydrogen embrittlement of high strength aircraft alloys, which would be high-strength steels which are typically used in landing gear, or, in the case of a helicopter, rotor components.



Simple Green does have an aircraft cleaner. Pure aluminum is very corrosion resistant, but has very poor mechanical properties. Aluminum is alloyed with other metals to give it higher strength. Aircraft aluminum alloys are some of the more corrosion-sensitive, due to their high-strength alloying tradeoff. The metals referred to on the Chinook are not typically found in a car, however, care should be excercised with any cleaner.
 
Setec, sorry for the wording error....that's what I meant to write. Not sure if I can edit the title.



At least people can view the info and make an educated decision on the product in question.
 
Tom, these kinds of corrosion (control) issues are common in the aerospace business. Aircraft are highly stressed vehicles, and they can't be made more robust without increasing weight to excess. Materials are specialized, thinner, have planned lifetimes, etc. IMO, you have a lot more to worry about on your personal vehicle from road salt than from any cleaner you could apply. That's not to say that from an appearance standpoint, any number of products couldn't stain/damage your vehicle.



I'm not sure that you could really hydrogen embrittle a high-strength steel with Simple Green, but a real concern with the aircraft aluminum alloys is stress-corrosion cracking (SCC) where a part under stress fails (at an unexpectedly low stress) in the presence of corrosive elements; see here or here.
 
I stopped using Simple Green a while ago as I noticed dulling of most things I used it on. I switched to TOL's Xtreme APC with excellent results.
 
daves745t said:
I've always been a fan of Simple Green - but there is no doubt that it is strong stuff.
Click to expand...



Yeah, it's strong stuff, but wouldn't Castrol Super Clean be even stronger stuff? Simple Green has a ph of I believe 9.3-9.5, while Castrol's ph is around 12 or 13 I think. So, knowing this info why does Simple Green get a bad rap?
 
Simple Green is corrosive and will react with bare aluminium causing hydrogen embrittlement (this is also known as stress cracking corrosion). As the cleaner gradually ferments it reduces the pH from its normal mildly alkaline state to acidic. Slow corrosion of the aluminium results, generating a little hydrogen on the surface.



Anaerobic conditions also generate hydrogen and hydrogen sulphide bio chemically, producing small amounts of methane. The aluminium probably has sufficient residual stress to be susceptible to hydrogen stress cracking, and this can be accelerated by the sulphide.



A ‘safer’ alternative Simple Green® Aircraft & Precision Cleaner - http://industrial.simplegreen.com/ind_prod_ext_mor.php



Meets Boeing Specs –D6 – 1748-7P (Water - based, no Hydrocarbon solvents)



[EDIT: added 12.06.12] Simple Green FAQ - Frequently Asked Questions
 
Ah, nice to see a thread about this topic getting bumped! People just won't quit using that stuff...at least not until they have it bite them.



Oh, and Welcome to Autopia, Coralsee!
 
Yes, Accumulator, this information/discussion seems to surface every year with more "newbe" Autopians coming on board.



I cannot stress enough that OTC Simple Green is NOT a safe degreaser/cleaner for use in today's cars that utilize so much aluminum. All it takes is one misuse of this cleaner because it's inexpensive and commonly sold everywhere and highly touted as a "safe and effective" cleaner, that the uneducated/ignorant user WILL cause damage to those aluminum parts and wonder why. I was one of those users for a LOOONG time until I read the information about it causing aluminum blume/fading/whitening/hydrogen embrittlement within this forum, maybe 6 years ago.



One thing has always puzzled me, though: if it is so bad for aluminum, why aren't there any warnings or caution notes on the containers/bottles?? I guess it would really cause a decline in sales.



I DO still use it, though. It was originally designed to clean coffee roasting equipment and I clean my coffee maker carafe and strainer with it and coffee cup at work, as well as counter tops where my coffee cup has spilled. It IS a good general purpose cleaner in that respect.



There are so many automotive-safe All-Purpose Cleaners (APCs) available, why risk using Simple Green. If you need something effective and available over-the-counter (OTC), just go to the local Harley-Davidson motorcycle dealer and pick up some S100 cleaner (P21S equivalent). Granted, it's much more costly, but it's much safer and more effective than Simple Green.



(Daja Vu all over again!)
 
Yeah, I wish I had taken pictures of various sets of wheels that Simple Green has severely dis-colored. I will the next time I see it.
 
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