Detergents and SCC/embrittlement 2

[gfbotha]

For health & environmental reasons we are considering using water based specialised detergents to degrease high strength aerospace materials like aluminium 7075 & marage steel used for critical applications. We are concerned about the detergents possibly causing SCC and/or embrittlement. The materials are typically cold/hot worked and in the case of the steel, welding is also done. Cleaning with the detergent will always be followed by a de-ionized water rinse/spray-off.

The suppliers of the detergents are quite protective about their formulations and we do realise the proper way would be to do extensive testing.

Would appreciate if anybody has any experience to share on the above. Any successes stories?

Thanks

 

[CoryPad]

Since you are dealing with materials before their end use, you need to worry about residual stress rather than applied stress. Usually residual stresses are lower, so if you rinse thoroughly and within a short time period after exposure to the detergent, you shouldn't have problems.

Embrittlement of steel usually is associated with acid cleaning or electroplating, however there is a small risk with any water-based process (such as phosphating). You can perform deembrittlement such as that described in SAE/USCAR-5 AVOIDANCE OF HYDROGEN EMBRITTLEMENT OF STEEL.



Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

If go you with a reputable supplier of metal cleaning compounds that are formulated for you specific soils and materials there should be no problems. That said, there has be installed a system that will insure that the cleaners are used according to the manufacturers directions. If the compounder of the cleaning compounds will not cooperate with you I would change suppliers.

You should check as there are some specific recommendations for cleaning materials in some of the aerospace specifications.

We clean all types of metals with numerous cleaning compounds and the only time I've seen any problem is when someone takes it upon their self to improve the process.

 

[TVP]

gfbotha,

I agree with the above comments, but also want to point out that different cleaners may need to be used for the aluminum and steel parts. Have you consulted the appropriate SAE aerospace documents or free resources like MIL-HDBK-509, DEF STAN 03-4/4, etc.?

 

[gfbotha]

Thanks for the valuable comments & tips so-far.

TVP, thanks for referring me to those documents. We have a consultant/contractor involved with this “New Wash Bay” project but I need to check and ask the right questions.

Would be a pity if we indeed need two different detergents (flushing the system before switching over, etc.).

BTW, I also reasoned it will be wise to dry the components immediately after the final rinse.

Regards

 

[gfbotha]

unclesyd, if possible do you mind please elaborating a bit on "...some specific recommendations for cleaning materials in some of the aerospace specifications", or should that be covered by the type of docs mentioned by TVP?

So, it is nothing new to clean the specific 2 materials I mentioned by using detergents (in the aerospace industry).

Any supplier(s) you feel like recommending?

Thanks

 

[CoryPad]

Henkel or Oakite-Chemetall.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

In addition to the two suppliers mentioned by CoryPad here are two more that I've had success with in cleaning metallic components.

Your concern about a separate bath for each component is valid. Depending on the soil that you are trying to remove it may require two separate cleaning lines. This will have to be worked out with your chemical supplier.

Some of the aerospace specifications give guide lines to the class and type of materials that can be used. I've seen several that have specific recommendations. Again, the chemical supplier should be able to assist you in that regard.

A word of caution.
At present they are some pretty aggressive people operating in the chemical cleaning supplier's sales force so watch out for the traveling used car salesman pushing chemicals. If you find one of these back off and go elsewhere.

http://www.espi-metals.com/metals/catdecontam.htm

http://www.heatbath.com/heatbath/product_details/7