Vapor Degreaser: Should we use TCE or PERC or Other?

A. Rosemary, For discrete parts, there are many methods for measuring the tin coating thickness on steel, such as beta backscatter, eddy current, coulmometry, and X-ray fluorescence, etc. I guess you are interested in a continuous monitoring method for detecting the tin thickness deposited on a steel strip. This requires a non-contact on-line methodology. An alternative for ellipsometry is X-ray fluorescence (XRF). However, XRF involves X-ray. So safety regulation should be concerned. Good luck! Ling

Ed. note: We edited Ms. Martin's inquiry to make it a bit clearer, after Mr. Hao's response. So if his answer looks a bit tangential, it wasn't his fault, we pulled the rug out from under him by changing the question he had answered.

A. We, at Corus also measure the oil layer at tinned or chromed material. Another solvent is Vertrel of Dupont (anout $50/ltr). An alternative, environmental friendly method is the hydrofilic balance. This equipment is automated by Mr. Kleyn of Rasselsteyn, Neuwied, Germany. A perfect instrument. Measuring time is more time consuming in relation to ellipsometer. About 3 minutes a sample.

A. In response to Thomas Gradolph's enquiry regarding the phasing out of Trichloroethylene to the best of anyone's knowledge there is no date for this to happen. The product has been banned in Sweden and this ban was upheld by the European Court of Justice plus in Europe TCE has been reclassified as a Class 2 Carcinogen with a Risk Phrase Heading of R45 'May Cause Cancer'. Under the new EU Solvents Directive the levels that will be allowable to be emitted to atmosphere are 2 milligrams per metre squared up the vent stack or 0.364 parts per million. These levels are impossible to achieve in most of the existing equipment used in manufacturing today. There are also moves afoot to re-examine the usage of TCE in the US. All in all this is a difficult subject with a great deal of conflicting opinions and data. The one thing for sure is that it is going to get progressively more difficult to use the product. There is plenty of information on the internet perhaps some of the most revealing can be found if you enter the words 'neurotoxicity trichloroethylene' on any search engine. You might not like what you see but it is very informative.

For many applications, Leksol is a direct replacement for Trichloroethylene.

A. Enviro Tech International produces solvents that would work in your application.

Regards,

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Ed. note: This is a technical discussion forum. To the maximum extent possible, please name the chemicals you are talking about, not trade names, nor companies who offer solvents. Thanks!

A. In the USA a few years back TCE was decided to be bad for human health. Many people switched to TCA, a very minor change. Then TCA was declared bad for the ozone and miracle of miracle at nearly the same time, the gods of government decide that the lab rats liver does not function the same as a human one and that TCE is not "all" that bad.

Perc requires some changes in your degreaser to use it. Its boiling point is higher so you have to reset the safety thermostat as well as the main thermostat. This requires that you also put more heat into the system as the "latent heat of vaporization is higher". If you had 12 KW with TCE, you probably would need 15 KW with perc. This is from a long long time ago memory, so check the actual numbers with the Mfgr. of your unit.

A fringe benefit is that it is easier to knock down the vapors at the top of the tank, so it should use less solvent.

A negative point is the amount of heat that the parts absorb. Costs more. Also, if it does not completely remove all of the "dirt" on the part, the higher temperature has a greater tendency to bake on.

If you were removing heavy oils or masking wax, I would certainly recommend perc. If not, it is a tossup. Only testing the process will yield the manufacturing answer. If you really tweak the system and follow all of the good practice rules, you definitely should put less organics into the atmosphere PROVIDED your parts do not "cup" the condensate.

A. If environmental impacts are your biggest concern, have you considered using a alkaline aqueous cleaner? There are many products available that do a good job removing light oils from aluminum parts, with little or no impact on the environment. Our company has made the switch to aqueous cleaners for our anodizing line many years ago, and its had no impact on quality, and eliminated the hazardous waste generated by using a vapor degreaser.

A. As a degreaser manufacturer, I have to say that we prefer TCE to Perchloroethylene for a number of reasons. Although one of the posts mentioned that you would need to increase the heat input, it did not cover the fact that many degreasers have integral refrigeration systems. The refrigeration system is designed to match the heat input that was originally supplied with the machine. If you simply increase the heat on one of these machines, the refrigeration system will be undersized, and vapors will rise above the cooling coils and out of the machine.

Another concern with perc, is the fact that it reacts with aluminum to create an acid. The acid can eventually contaminate the entire machine, and corrode even the best grades of stainless steel. This is not a serious problem if the parts are chip and dust-free, and if the only contaminant is oil. In that case, the parts are the only aluminum being exposed to the solvent and they are generally not in the solvent long enough to cause a problem. If however, the parts have even the smallest amount of aluminum dust or chips adhered to their surface, the chips and dust will accumulate in the bottom of the boil or rinse compartment, where they will begin to react.

Thank you for your help.

I will first try the aqueous degreaser and only use the TCE if water doesn't work.

A. There are several factors which may turn your company in one direction or another such as the required temperature needed to perform the requirements. As I have investigated and worked with "PERC" the regulations set in the United States are readily available which are designed to contain the vapors whether they are Perc or any other substance. The alternative that I have seen that is rated non-hazardous is N-Butyl-Bromide which has a trade name of Detride manufactured by Detrex and after several parts tests the results were very much the same as with PERC but the cost was about 4 times that of PERC. The environmental concerns can be eliminated by proper containment in your facility.

A. If you are considering an aqueous degreaser, there is also an acid cleaner to be used in place of the alkaline cleaner that I have had success with. Check with your supplier.

A. Try asking your normal chemical supplier or try some new ones. Bulk acid suppliers will often sell drums of trike.

A. While looking for Degreasers I found your question. I have been in the cleaning business for 15 years for Aerospace. Since the reduction of CFC's we have found alternatives to other solvents. HFE-7100 is a good replacement and environmentally friendly. You may look into this for your operation. Aqueous cleaning is also an option and we have had great results.

A. We would advise to go for hybrid cleaning to avoid harmful solvents. One can use aqueous cleaners in first two or three stages followed by water displacement solvents where all the water is taken out & finally rinse it with solvent vapors. These days solvents like Leksol & Ensolv are readily available in the market which are eco-friendly & 1 to 1 replacements for TCE/ PCE. We have implemented such hybrid cleaning in number of units successfully.

A. Using TCE (trichloroethylene) is not a good idea as it has been identified as a possible carcinogen (i.e., may cause cancer). It was originally favoured as a replacement for the more harmful trichloroethane, which was banned under the Montreal Protocol in 1989.

The Montreal Protocol tried to ban all ozone depleters as it will result in an increase in exposure to harmful UV radiation and an increase in cancers associated with exposure to the sun etc. Unfortunately some national governments have not seen it worth their while to preserve the Earth, so I suspect they must originate from another planet.

Nevertheless, trichloroethylene has now been identified as also being a possible carcinogen and it too is being phased out, albeit voluntarily. There are numerous substitutes that may be suitable, but unfortunately both trichloroethane and trichloroethylene are extremely good at degreasing parts! One possible substitute is n propyl bromide (nPrB or 1-bromo propane), but this has a disadvantage that it is a very strong irritant to the mucous membranes and the skin - consequently it has a very low exposure limit of 25 ppm TWA. However, it does not appear to be a carcinogen nor an ozone depleter. Many other degreasers are available, but it is more of a "horses-for-courses" scenario. There are numerous aqueous based systems around that may or may not use ultrasonics, or you can use solid CO2. It all depends on what you want to clean and what the contaminant is. To combine TCE with nPrB doesn't solve any of the problems of the materials, in fact it compounds them and makes things worse because you are using two very unpleasant materials instead of one! nPrB is overall better than TCE, but you still need to take special precautions. I would suggest you look for a totally different cleaning system, such as an aqueous or semi-aqueous one, or even CO2. The problem with the internet is that what is available in one country may not be available in another, so I suggest you discuss your problem with a reputable, global, chemical supply house.

2003 Now, Trevor ... Maybe it's not that some peoples don't want to save the earth, but the usual issue that people define fairness from different perspectives -- the age-old issue of whose ox is being gored. Millions of we Americans have paid many hundreds of dollars each to retrofit our automobile air conditioners because we can no longer re-charge them with ozone-depleting substances -- while most of the world faces no such restrictions. Americans have accepted that we cannot replace old refrigerators or freezers or home air conditioners until we first pay a specialist a substantial fee to come out and remove the freon for recycling, which must then be followed by standing in queues at city hall for forms swearing to & documenting said Freon recovery (I've been through this aggravation). Without the related sticker on it, it is not possible to dispose of those scrap appliances / scrap steel ... although few countries on the planet do anything even remotely similar. Yes, we resist a protocol that says that if our child suffers an asthma attack and is clutching desperately for a breath, that s/he may not use an aerosol, but may only attempt to relieve their suffocation by inhaling powders, hoping that some of that powder can make it to their lungs rather than it all sticking to the wet insides of their mouth and throat). And while our afflicted children are denied this milligram of freon in an inhaler, the later-developing countries like Argentina remain free to wash their automobile parts in open pails of ozone-depleting substances out in the street. Yes, I realize it's only for a limited number of years, and blah, blah, blah. One point of view is that the Montreal protocol did not only say that CFCs are bad, but that America's businesses should be closed down so other countries can manufacture CFCs instead. Probably the main reason that America hesitated to sign the Kyoto protocol was because of what the Montreal protocol taught us: that such international resolutions are usually as much about bashing America as reducing pollution. It would be nice if these proposed international agreements didn't have the implicit preamble: 'Whereas Americans, being ignorant & lazy oafs, ...' While I admit to engaging in a bit of hyperbole, I challenge each reader to actually read the Montreal protocol before commenting (it's on the internet, and only about 6 pages long). As you read what various countries can and cannot do, form your own opinion about how much I am exaggerating :-) Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey

A. Dear friend,

While I debate the comments on the carcinogenic nature of TCE, I would like to emphasise the benefits and "cost" of TCE in comparison to any other means of cleaning. Perhaps, aqueous cleaning is an option, but it has a lot of limitations. We recommend aqueous cleaning in a variety of fields, but at times it is not the best solution if "cleaning" is not proper.

I give below a few facts:

Trichloroethylene has never been considered to be ozone-depleting and is not mentioned in any annex of the Montreal Protocol nor its amendments and is never likely to be. In 1999, 78,842 tonnes of TCE were known to have been used in W. Europe for solvents applications In 2003, the US production of TCE is expected to top 100,000 tonnes. If TCE were forbidden, then neither country would use so much. 2000 World production of TCE is estimated at about 500,000 tonnes.

However, I can guide better if I know the process and your consumption pattern. Just to inform you in a non-commercial way, we speak from experience. Meanwhile, don't waste your time in finding formulas in cookery books for mixing various solvents, its better if you go for God gifted products and try not to be inventive as it just might be more harmful to your workers.

A. N-propyl bromide is pretty close to being a direct replacement, but is very expensive. Many shops have converted to aqueous cleaning, but that is, of course, not without pitfalls itself.

A. I have not heard that TCE will be prohibited. Of course nPB can directly replace it without modification of vapor degreaser. But the price of nPB is more expensive. If you can keep the workshop under good ventilation, TCE is still a good solvent for removal of oil and grease from metal parts.

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Ed. note: See update from James Simmons, January 2015

A. If your vapor degreasing machine does not emit any vapors, there will be no problems. Here in California, we were excluded from the ban because our machine did not emit any vapors.

A. Most of the degreasers built for TCE in the last 20 years have very poor solvent vapor containment. TCE has always been an inexpensive material and the manufacturers have not had any motivation to reduce consumption. Modern equipment designs can reduce emissions from vapor degreasers by up to 90% in some cases making TCE emissions much less and the workshop concentrations of TCE very small indeed. The practice of inducing a forced ventilation just made the emissions from poorly designed degreasers worse and only moved the problem outside the workplace.

A. Methylene Dichloride.

A. Hey There

Have a look at Shell Chemicals or other petrol companies web. They offer a wide range of low boiling solvents, which will be a good substitute for TCE.

K Regards,

A. Hello Jayshree. Aqueous cleaning is often possible as an alternate, and n-propyl bromide is a good but expensive solvent for vapor degreasing. But there really is no such thing as a general substitute for a chemical, only a substitute for a chemical in a specific application; please describe your application. Thanks!

A. That has been the subject of numerous books and hundreds if not thousands of technical articles over the last few decades, Vinay, so it can't be summarized in a paragraph ... but n-propyl bromide is pretty close to a drop-in replacement.

A. N-propyl bromide is probably the closest thing to a drop-in replacement, Shan. But there has been a very strong movement to try to get away from solvent cleaning and into aqueous cleaning when possible. Good luck.

A. AT THE FERNALD URANIUM REFINERY FMPC in 1953 we replaced trichorethylene with trichloroethane in degreasers.

A. nPB is a neurotoxin and a carcinogen that is extremely unsafe for operators near a vapor degreaser. The ACGIH has an exposure limit of 0.1 ppm (8 hour TWA), which vapor degreasers cannot satisfy unless they are vacuum vapor degreasers. Law firms are soliciting for clients to sue firms that use nPB in a vapor degreaser.

Novec 72DA is available and used in India as an effective degreaser solvent. It is a drop in replacement for TCE for vapor degreasers. It has an exposure limit of 200 ppm.

A. Hi James. Thanks for the update on n-propyl bromide. This crazy game of whack-a-mole continues through the decades.

Luck & Regards,

A. Hi Gopalan,

We are not toxicologists here, so any argument on toxicity will be from available literature, rather than from expertise knowledge...hence treat any comment with a little caution.

TCE is classified as a carcinogen, which means it may cause cancer in humans. Cancer causing agents tend not to cause cancer after a single exposure, but over multiple exposures over longer periods of time, sometimes into 10s of years.

TCE is also narcotic and an asphyxiant, so must not be used in enclosed condition. There will be a national occupational exposure limit that must not exceed.

So, yes, TCE can be harmful, but it does depend on how you use it and how you protect your workers from exposure.

There are all sorts of processes that could potentially replace TCE, from simple solvents such as iso propyl alcohol and acetone ⇦this on eBay or Amazon [affil links] Warning! highly Flammable! , to aqueous solutions, to mixtures such as Vertrel or Novec HFEs, to more complex alcohols used in special kit. Whatever you do, you must comply with your country's laws on these chemicals.