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topic 4275

Solvents used in vapor degreasing




An ongoing discussion from 2000 through 2014 . . .

(2000)

Q. Hi. I am an environmental engineer and work for a consulting firm. I am trying to find some information for a client who conducts vapor degreasing of stainless steel after it is formed into a product. I am trying to determine when they likely switched from TCE to TCA. I have found information indicating that, as of 1969, TCA was not used for vapor degreasing because suitable stabilizers had not been developed/identified. Does anyone know when these stabilizers were found and when TCA was first used for vapor degreasing? Also, does anyone have specific information regarding the stabilizers historically used in TCA and TCE?

Sarah Levin
- Milwaukee, Wisconsin


(2000)

A. If my understanding is correct, you are predicting when your client changed from TCE to TCA, rather than getting the stabilizers history. I don't think the reason of late emergence of TCA compared with that of TCE was due to the stabilizer. In fact the stabilizers present in industrial TCE and TCA are the same. TCE has a better cleaning ability than TCA. This accounts for its earlier industrial use. However due to health and safety reasons, TCA which has a lower toxicity gradually replaced TCE. Eventually scientists discovered that TCA is ozone-depleting (environmental concern) and TCE came back.

Perhaps both you and I are too young to remember the stories in the '70. Sorry that I can't provide you an answer to your question. Hope that you could have got some idea here for your searching.

Good luck.

Kwok-wai Chook
- Hong Kong, China


(2000)

A. Sarah, I do not know but I know who to ask! Call Dow Chemical, they should be able to easily supply at least the information on TCE if not both solvents.


Megan Pellenz
- Syracuse, New York


(2000)

A. The stabilizers in TCE and TCA are not identical, they are generally similar, and do use some of the same material. TCE will withstand much more water before it degrades than TCA will. Bond strength is higher. Water in hot solvent breaks off the chlorine (s) and forms HCl, or hydrochloric or muriatic acid. When hot, it pits the ----- out of stainless steel.

TCE has better solvency of some soils and operates at a higher temp, so generally cleans better and is easier to trap because it is easier to cool to the condensing point.

About 1983, the US govt changes TCE from a suspected carcinogen to a probable carcinogen. Because of health issues, companies bailed out of TCE in droves.

The Montreal protocol was the kiss of death for the use of TCA because of ozone depletion.

At virtually the same time the Govt says "oops" TCE is not as bad as we thought because the human liver does not react the same as our white mice do.

Therefore, TCE is the degreasing solvent that is mainly used now.

James Watts
- Navarre, Florida


(2005)

Q. Sorry to come into this discussion several years down the road. I have a question for Ms. Sarah Levin, Milwaukee, WI. You mention in your 1/19/00 text that you've found information indicating that TCA was not used prior to 1969.

I too have a client that used vapor degreasing in the sixties. We're trying to definitively determine if TCE was essentially the solvent of choice in that decade.

I'd appreciate further conversation. Thanks

Bob Mussro
- Warner Robins, Georgia, USA


Solvent pollution suits: your name is legion :-)

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



November 3, 2014

Q. I would like to know what is the best cleaning system for automotive brass turned components. Vapor degreasing solvent TCE is banned in USA and Europe? If yes, please suggest another equaling solvent for vapor degreasing.

Himen Baldha
brass industry - Jamnagar, Gujarat, INDIA


November 2014 opinion!

A. Hello Himen. PERC and n-propyl bromide are two that I can think of. But the truth is probably that the environmentalists and the solvent manufacturers are playing whack-a-mole, and that the new European REACH standards will become a bridge too far for any vapor degreasing solvent.

It can be difficult, but switch to aqueous cleaning.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


November 4, 2014

A. Hi Himen,

Under the EU REACH regulations both n-propyl bromide (nPB) and trichloroethylene are listed as Substances of Very High Concern (SVHC), with trichloroethylene being now on the Annex XIV Authorization list, with a sunset date for use somewhere in 2016, after which it will be illegal to use the material in the EU without an approved authorization.

Now, there is nothing stopping you using it in India and then shipping your product into the EU as there will be no offending solvent on the parts when they arrive in the EU. As far as I am aware the USA doesn't have any bans on the use of trichloroethylene, although it is frowned on, there is also no worry about the use of nPB currently.

Perchloroethylene is currently not covered by REACH, but to be honest it has an R-40 phrase so is likely to end up on the SVHC list, as is methylene chloride.

Of course if you are looking to "future-proof" yourself you need to look for a solvent with low toxicity, not rated as a carcinogen, mutagen, reproductive toxin, endocrine disruptor, bioaccumulative toxin, low global warming potential, non-ozone depleting...best of luck with that one!! You can look at the products based on trans-1,2-dichloroethylene with either Hydrofluoroethers (HFEs) or Hydrofluorocarbons (HFCs) (be careful of the EU F-gas regulations though) or possibly a new set of solvents based on Hydrofluoro olefins (HFOs).

Brian Terry
Aerospace - Yeovil, Somerset, UK


November 5, 2014

Q. Many Thanks for your prompt response.

If we clean the components with your suggested solvent how long it will remain stain free if kept in proper packing?

Himen Baldha [returning]
- Jamnagar. India


November 7, 2014

A. Hi Himen,

It will stay clean as long as it is not in contact with any contaminants, which can be as simple as finger prints to deliberately added corrosion protective oils.

How long will it stay corrosion-free, well that is a different question and will depend on the storage conditions. If you store in a high humidity environment then the brass will certainly tarnish, and will probably corrode.

Brian Terry
Aerospace - Yeovil, Somerset, UK


November 2014

A. Hi. Brian has answered your question, but I would add that it is possible to use corrosion inhibitors such as VCIs in your packaging, or to dip the work into sodium benzotriazole before packaging to extend the stain-free life.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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