Alternatives to trichloroethylene to vapor degrease parts

A. Well, there are some new and very expensive proprietary "non-CFC" vapor degreasing solvents as alternatives to tri-chlor and TCA. But the basic thrust of the movement has been to try to switch to aqueous cleaning when possible -- almost always possible for steel parts, more difficult for aluminum, and quite troublesome for mixed metal.

A. A think a lot depends on your application. For some you might try one of the aqueous or citrus degreasers but for some applications I have never found anything as a specified alternative. I hope someone can correct me because I would love to find an alternative too. I know some of the studies failed because of residues on the items.

A. Nothing will ever be as effective as good 'ol tri-chlor! There are fluorinated solvents that work extremely well. Only problem is that they are quite expensive and evaporate at an even faster rate than tri-chlor. So a lot of your $$ disappears, so to speak. If your application is somewhat of a closed environment, though, they may be worthwhile.

A. Alternatives to trichloroethylene (TCE) are becoming essential, especially in Europe where the compound is now classed as a Category 2 carcinogen with an R45 risk assignment.

There are two possible options open:
1) switch to an alternative solvent for vapour degreasing such as
a) perchlorethylene (PCE), which has a lower health risk (R40) and fewer penalties for use, or
b) stabilised n-propyl bromide, which carries only an R20 health risk.
2) switch to aqueous cleaning.

The first option has a number of benefits over aqueous cleaning and in stand alone situations where the cleaning is not followed by further aqueous processes, it can be demonstrated to be more environmentally sound. N-propyl bromide is widely gaining acceptance as a drop-in alternative to TCE, including a number of aerospace companies such as BAE Systems, Airbus, Lockheed-Martin. Boeing is however still testing for approval. It can give cost benefits over TCE and is also safe to use on oxygen system parts and in electronic applications. The latest information I have indicates that it is about to get a SNAP approval for metal cleaning applications.

Regard,

A. Probably your question should contain details about the base metal. The type of oil you get on the parts? Mineral oil? or any other? Volume of material you clean, etc.

In general there are few aqueous solvents which contain chelating agents and saponifiers which can be used for this purpose. You can contact some plating chemicals suppliers who will have the recipe ready for you. IPA can be used but if will not be as efficient as the TCE for the cost you put.

Ferrous material can go for series of alkali cleaning if your system is equipped with oil skimmer.

Good luck ..

A. Hydrocarbons are compounds of hydrogen and carbon, the best example being gas and oil and other petroleum products. Please talk to a distributor of industrial metal finishing products, Malcolm. They can introduce you to alternatives ranging from drop-in replacements to switching to aqueous cleaners.

A. Trichloroethylene replacement is fairly complex. Specifically as there is pressure to move away from VOC's. However a range of solvent types can be utilised from hydrocarbon (least effective) modified alcohols, esters, etc.

A. Have you considered plasma cleaning? Plasmas are a dry, environmentally friendly alternative to solvent cleaning/degreasing, use no harmful chemicals and produce ultra-clean surfaces with complete removal of organic residue.

A. We use tons of TCE as of now for degreasing the metal stamped parts and deep drawn parts used in motor making.
Aqueous is bit risky if not done properly. As such we tried several alternatives and for one application we could use MTO instead of TCE..
TCE is a wonderful degreasing agent and nothing is as powerful as this.
We are in the process of trying Acetone and yet to see the success.

Uppili
India

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January 2010

!! Readers please note that Acetone is flammable though! Maybe not a big issue when applied with cotton Q-tip [affil links], but a significant concern when "tons" are used in a big open tank in a production environment.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Portia,

It is so difficult to have a truly "REACH compliant" solution to TCE as the goalposts keep moving. In the short term you could consider perchloroethylene or methylene chloride, these have similar solvency to TCE, but different boiling points. These both have a R-40 risk phrase, so eventually will end up on the SVHC list.

n-Propyl bromide is probably not going to be around as a cleaner much longer as it has an R-61 classification in the EU nowadays and will end up on the SVHC list sooner rather than later.

You could consider the HFEs as marketed by 3M or the HFCs as marketed by DuPont. These are considerably more expensive than TCE, but are unlikely to be caught by REACH too soon (although watch out for the F-Gas regulations).

Of course you could move away from solvent cleaning altogether and look at aqueous cleaning. Aqueous technology has moved on a huge amount in the last few years and combined with the correct equipment can be just as effective as solvent cleaning. You are better off talking to local reps about this possibility as there are a lot of companies manufacturing aqueous cleaning chemicals.

You could look at some of the more exotic technologies such as plasma cleaning or dry ice blasting. These are likely to have a cost implication, but may well be worth looking at, even if you don't go down that route.

Finally you could move away from cleaning technologies that may need the use of expensive chemicals and/or equipment. If the geometries are simple then simple swab degreasing with one of the many solvents marketed for this process may well work for you. Look at the iso-parafinnic hydrocarbons, these have become quite popular over the last few years for swab degreasing. You could always go with some of the more common solvents such as acetone, MEK, iso-propyl alcohol etc, but be warned these are highly flammable so need special precautions for use.

Hello Portia,

I am confronted with this type of question on a daily base, having lots of well-known customers in aerospace.
Wherever an ECSA Type IV or V machine is involved, normally it should be no problem to re-adjust the machine from usage of Trike and Change to Perc.
Perc is the best solvent next to Trike and in 95% of all applications usable.
Type V hermetic sealed degreasing machines operating under vacuum also come very close to the temperature range of Trike.
So-called "alternative" solvents like the HFE,HFC and npB are practically not usable in state-of-the-art machines according ECSA IV and V, only in the old style open-top machines with the related emissions and running costs for continuous consumption and refill.
In Europe they are absolutely minor in number of applications.
Trend in Aerospace is usage of Perc and modified alcohols.
-> for sustainable usage but only in most modern equipment, emission free.

See the recent discussion going about cost pressure in aerospace-manufacturing coming from the carriers down to the manufacturers and their suppliers:
A replacement of Trike by just seeking a solution in a complex and expensive aqueous machine in operation and quality control, just to be virtual more "green", does not help.

BTW: we offer aqueous as well, where it is suitable on application.
Certainly not on composites and also not where NDT is involved -> solvent is the answer.

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,

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).

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?

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.

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 [on eBay or Amazon] before packaging to extend the stain-free life.

Regards,

A. Hi Rachel,

Can't comment on timelines for EPA regulation, I'm on the wrong side of the pond. n-Propyl bromide is already heavily regulated in the EU, with it first of all appearing on the Registration, Evaluation, Authorisation (and restriction) of Chemicals (REACh) regulations Candidate list of Substances of Very High Concern (SVHC) and then accelerated to the Annex XIV Authorisation list. It has a sunset date of 4th July 2020, after which time it will be illegal to use the substance, unless there is a valid Authorisation in place, or an Application for Authorisation (AfA) has been submitted.

So, this side of the water people have gone in many directions. By far the most popular option has been aqueous. Away from the chlorinated solvents common solutions have involved a mixture of trans-1,2-dichloroethylene and certain fluorinated solvents (HFEs and HFCs), available from companies like 3M and DuPont. Single component fluorinated compounds are not particularly good degreasers, but trans-1,2-dichloroethylene is good, however it is flammable, hence why it is not used on its own. Then there are HFOs, these are either used as a single component or cut with 2% methanol [affil links] to increase polar contaminant degreasing ability.

Saying that, the Non-Government Organisations (NGOs) are now after fluorinated compounds as they are considered persistent polluters (no evidence of toxicity, but why let facts get in the way...), so I'm guessing we Europeans will be looking for new technologies again, much sooner than I'd hoped...

 Thank you Brian for your detailed response. We are impacted by REACH as it applies only to finished products but the wording of the regulations may impact our processing anyway- this is another thing I need to work on, lots of reading catch-up, and I ALREADY can't find my desk :/
So it seems, as I suspected, that any of the halogenated solvents are going to be off the table sooner rather than later. *Sigh.

A. Hello Rachel

The search for a TCE replacement continues with us as well. It is good to get this discussion moving in regards to a viable longterm replacement to TCE. We are looking at (t-DCE) as a drop in replacement.

(hydrofluoroether methyl nonafluorobutyl ether (C4F9OCH3), ethyl nonafluorobutyl ether (C4F9OC2H5), trans-1,2-dichloroethylene (t-DCE) and isopropanol)

I have found there are not a lot of options. Currently using TCE in a shiny piece of equipment as well. We are also using Aqueous Ultrasonic and DI water rising methods to clean parts.

I am interested in any comments regarding the long term performance of the (t-DCE).

It will become more important than ever to control the soils that are entering your process if aqueous becomes the best practice.

The current TCE solvent solution allows for a level of confidence in cleanliness results.

Great discussion.

A. Hi Jagdish. It probably won't hurt the aluminum, but may not be the best answer to your overall situation. Please tell us who you are and what's going on. Thanks.

Regards,