Trichloroethylene/TCE in Metal Finishing History Q&A

A. Hi Aty. TCE is probably most frequently used in a 'vapor degreaser' rather than in an immersion or solvent wiping situation.

A vapor degreaser is an open-top tank which basically has three vertical levels:

- The bottom level is a reservoir of liquid which is heated so that it fumes. The work may or may not be initially dipped into this reservoir.
- The middle level is where most of the work is done. Objects to be degreased are cold or at least room temperature, so when they are lowered into that middle level the vapors condense on them, then run down into the reservoir, ideally carrying away the dirt and grease.
- The top level has refrigeration coils which cause the vapor to condense and fall back into the reservoir instead of escaping into the environment.

But as you might surmise from the thread we've attached your inquiry to, vapor degreasing with trichlorethylene is not nearly as common as in bygone days. These days aqueous cleaning is done instead whenever it is practical, and it's almost surely practical for steel plates which will be electroplated. Use the search engine to browse around for "electrocleaning".

Luck & Regards,

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.

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.

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.

A. PCE has been used for many years to remove wax masking film from plated parts. TCE was a very common vapor degreasing solvent in most plating shops. Conversion from TCE to TCA was the result of USEPA pressures in the early 80's.

Then the Montreal Protocol took effect, with ozone depletion a bigger worry than carcinogens, so TCE is in favor again. EPA decided that a human liver was not the same as a lab rat and that TCE was not that big a problem.

A. The company that I worked for switched in 1981. Talk to the good folks at Dow Chemical. They were the largest manufacturer of TCE and did the lion's share of proving that is was not severely carcinogenic to humans, just lab rats.

A. "Products Finishing"magazine had an excellent multi-part series on vapor degreasing--a column as I recall--written by J B Durkee. I think it will contain exactly what you're looking for.

A. Anything is possible. Since aluminum dust is bad news in a vapor degreaser, I would not give it a very high probability.

A. Hi. Bright dipping is usually done in a phosphoric acid / nitric acid mix, but as far as I know it would be one step in an anodizing process, and vapor degreasing is pretty widely used for cleaning aluminum despite the problem Mr. Watts mentions because other cleaners can be problematical. For example, electrocleaning, which is widely used on most other metals, can't be done on aluminum; aluminum will get deeply etched by the strong caustic aqueous cleaners used on other metals; and mixed metal processing in aqueous cleaners causes galvanic corrosion of aluminum. So I think chances are actually pretty good.

Luck & Regards,

A. TCE was quite likely to have been employed in the finishing of these parts because it was the preferred solvent in vapor degreasers for a couple of decades, and vapor degreasing is good way to start the cleaning and finishing process.

A. The June 2000 (Volume 1, No. 2) issue of the journal, Environmental Forensics, has two articles that summarize the history of chlorinated solvent use. These can be obtained at: www.environmentalforensics.org/journal/volume1/number2.htm Good Luck!

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Ed. note Dec. 2021: That page no longer works, but those articles are referenced on archive.org's Wayback Machine at https://web.archive.org/web/20050309200207/www.environmentalforensics.org/journal/volume1/number2.htm
It is available from some of the standard paywalls offering research articles, or if you have good eyes plus infinite patience with dismissing pop-up ads it can be viewed at www.yumpu.com/en/document/read/39835629/a-history-of-the-production-and-use-of-carbon-tetrachloride-

A. TCE was not banned in the 1970s, and, to the best of my knowledge has never been banned. What did happen is increasingly stringent limits on TCE discharges to air and water to the point that most people found it more practical to switch to other solvents or aqueous cleaners.

A. You have no options. You must drum it in legal drums, manifest it properly, ship it via a certified hazardous waste transporter to a certified disposal site. The site is licensed to recover some of it as a cold solvent and they typically burn the rest in a certified furnace. The simplest thing to do is contact a couple of companies that are in this business. Check with the states they operate in or thru to find out their track record on violations.