Once upon the time..we had an open 500 liters cleaning bath for degreasing
machined parts. There was a vapour evacuating tube above, but that was all.
The operator lowered the parts into the tank and let it be there for a few
minutes at + degrees (don't remember how much). A propeller caused the TCE
to flow around the details. It happened that someone lost the grip of the
lifting tool and the metal thing hit the vehicle's bottom. What to do?
Quickly put full arm lengt into the bath and get the component, and rinse
skin in water. Remarkbly enough, few employees were ill at that time. Not
that I recommend a return to such madness, just a fading away memory.
Alcohol is accepted limitlessly in every home, but not a few centiliters of
TCE. Even more mad.
There is more for the future purists to wow about....Just wait and see
when the first side effects of Viagra will appear..that cacaphony will
override TCE noise
Not a very logical thread, maybe because the glass of Famous Grouse I just
had....
Thanks for the good lesson about Titanium. Made me even more observant on
the case of phase displacements and built up "squamous" (isn't there a
professional word?) superficial phenomenons. On the q how to determin the
cleanliness, I think of simply boil the part in water and see if any fatty
debris flows to the surface. If someone got a better idea, you are welcome
to share with me.
To end this mail, I add something I didn't know before. A friend of mine is
from Iran and he speaks little farsi (old persian). I mentioned something
about chemistry and he asked " do you know what or where the word chemistry
comes from ?" No, I said. "It's farsi 'chemi' which means gold. 'Al-chemi'
means 'make-gold' . The later all know, but how many knew that chemist was
old persian language?
Inge
----- Original Message -----
From: "Brian Ellis" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, March 30, 2009 4:40 PM
Subject: Re: [TN] Titanium
Titanium is a funny metal. Fabricated items, such as snob-value watch
cases, are often sintered into a rough shape before machining, rather
than cast, as would be gold. This is because casting is very expensive
as it is done in a vacuum (hot Ti burns on O2 and N2 long before its
melting point!!!). Ti is extremely difficult to machine, whether
sintered or derived from a casting, but sintered is the worst. The tool
must be really perfectly ground without wear and the Ti must be really
well cooled (pumped cutting oil systems such as for steel or non-ferrous
metals are often insufficient). This is because there is a phase change
induced by pressure at temps above ambient, locally softening the metal
crystal-by-crystal and this causes the metal to deform onto the tool and
gall. This often 'snowballs' by minor galling inducing ever-increasing
deformation. I don't know all the ins and outs of Ti galling but I have
observed it as a severe problem in practice (in a former life, I
designed a part for working in HCl that had to be turned from bar; the
turner had hell's own job!).
I mention this because your "squamous" surface may be due to galling,
especially if the part is sintered, rather than cast.
As for TCE, I knew one of the guys who was behind the ban in Sweden. At
the time, I had long and heated discussions with him that he was making
a BIG mistake. I never was a fan of halogenated solvents but I always
admitted there were some applications for which they were indispensable.
The idiocy started in E Germany where a factory's employees had an
abnormal number of cancer cases ascribed to TCE. No epidemiological
study was made or confounding factors determined. It later transpired
that the TCE was stabilised with epichlorohydrin, a known carcinogen but
it was too late, Germany had already decreed TCE was a known carcinogen
in humans (MAK1) with a PEL of (I think) 1 ppm. For some reason, they
never wanted to correct this error, despite serious studies to the
contrary, and some other countries followed suit. FYI, perc, which is
potentially more toxic than TCE, is classed as MAK3 in Germany with a
PEL of 25 ppm. Carbon tetrachloride, which is KNOWN to be a lot more
toxic than TCE, is also classed as MAK3 with a PEL of 10 ppm. It simply
makes no sense whatsoever. I think you will find Germany's stupid
classification of TCE will reach REACH, if it hasn't already done so. To
get back to my Swedish colleague, he argued that all applications using
TCE could be replaced by aqueous cleaning methods. Memories of these
arguments still make me squirm; you simply could not have a scientific
discussion based on fact, he had a political point to make. At one
point, in a committee meeting with ~20 persons present, he was shot down
in flames by the consensus and he simply stormed out of the room,
slamming the door (this was c. 1989, when we were desperately trying to
promote all known means of cleaning using relatively safe non-ozone
depleting solvents, such as TCE, in preference to 1,1,1-TCA).
Would it be possible to use TCE in a zero-emissions machine? (Virtually
0 ppm in the workshop at all times, certainly less than 1 ppm.) Surely
that cannot be forbidden? It would also ensure compliance with the EU
VOC Directive.
Brian
Hernefjord Ingemar wrote:
> I reckon that some mineral oils seem to be very bullheaded. We had let
> parts pass aceton and etanol and some other cleanings, and to our
> surprise, after electron beam vacuum welding the two (cleaned)parts
> together, small and yellowish fatty things appeared on the liquid surface
> when the finished part was recleaned after the welding. This was done by
> dipping the flasklike part in a degreasing tank. Evidently, mineral oil
> was still hidden in the titanium surface after machining, despite it
> looked clean and left no debris when you rubbed with a white cloth. In a
> high magnification microscope you can see a lot of microscopic damages,
> void or what to call the rude surface. Just unlike steel and other metals.
> Whatever machining parameters or tools, it seeems as titanium is
> "squamous" after the drilling, milling etc.
> TRI...hmm...was cast out here twenty years ago...chemo textile cleaning is
> allowed to be done with perchloroethylene, which I find remarkable. The
> later is not better in a environmental point of view.
> Inge
>
> PS. VIGON 200 = 11-12 (pH)
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: måndag 30 mars 2009 13:04
> To: [log in to unmask]
> Subject: Re: [TN] Titanium
>
> I'm not sure that Vigon will be satisfactory for removing mineral oil
> residues and their additives, as these will not saponify in the amines.
> You will need something with the pH exceeding 12-13 and with stronger
> tensio-active components.
>
> I'll shock you by suggesting a trichloroethylene blend in a zero-emissions
> cleaning machine with a vapour phase final. I don't care what people say,
> it is a damned good low-cost solvent, used sensibly it is perfectly safe,
> it is non-carcinogenic to humans (it is carcinogenic to rodents in high
> doses, but their metabolism of the substance is
> different) AND IT WORKS!!! (If needed, I have details of epidemiological
> studies with cohorts of tens of thousands supporting my statements.)
>
> In the unlikely event that this alone would be insufficient for your
> needs, then consider an aqueous solution, depending on the residue
> analysis after TCE.
>
> Brian
>
> This alone would probably be sufficient and low-cost
>
> Hernefjord Ingemar wrote:
>> The tests will show. If one or two steps can be left, of course very
>> good. On the other hand, the cost for these units is so high, that some
>> dollars saving is negligible. Unlike the normal production when cents are
>> hunted for.
>> The alcaline bath will possibly be superseded by our Vigon 200 tunnel
>> cleaner. /Inge
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
>> Sent: måndag 30 mars 2009 11:28
>> To: [log in to unmask]
>> Subject: Re: [TN] Titanium
>>
>> Ingmar:
>> The process you suggest probably will work, but I suspect it is overkill.
>> I suspect that the alkaline cleaner will be enough on its own.
>>
>> Good luck.
>> Rudy Sedlak
>>
>> --- On Sun, 3/29/09, Hernefjord Ingemar
>> <[log in to unmask]> wrote:
>>
>> From: Hernefjord Ingemar <[log in to unmask]>
>> Subject: Re: [TN] Titanium
>> To: [log in to unmask]
>> Date: Sunday, March 29, 2009, 11:58 PM
>>
>> Thank you, Rudy&Steve.
>>
>> It seems as a suitable treatment would be this one:
>> a)Solvent degrease, followed by
>> b)Alcaline bath, followed by
>> c)DI ultrasonic bath, followed by
>> d)Micropowder blast, followed by
>> e)HNO3 dip, followed by
>> f)DI ultrasonic bath.
>>
>> We will try this today already. We do not like HF, so that kind of
>> process is skipped. Our problem is not primarily to remove the oxide, but
>> to ascertain that all threading/cutting oil is gone, also that the
>> numerous micro pores are emptied from their content.
>>
>> /Inge
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
>> Sent: lördag 28 mars 2009 20:19
>> To: [log in to unmask]
>> Subject: Re: [TN] Titanium
>>
>> Although Titanium lightly alloyed is used in some joint replacements, it
>> may well be more commonly known for its use as Nitinol, a Nickel/Titanium
>> alloy, which has weird "memory" properties. Nitinol is one of the more
>> common stent materials.
>>
>> Cleaning Titanium is quite difficult, particularly if it is heavily
>> oxidized, as the common "cleaning" agent, (Hydrofluoric Acid) attacks
>> Titanium vigorously, and then to frost the cake, this causes Hydrogen
>> embrittlement.
>>
>> Not everyone/everywhere is as "enlightened" as we like to think we are,
>> and yes, there is still choro-ethanes still in use in cleaning (Think
>> "dry cleaning" clothes).
>>
>> There are proprietary cleaners which purport to get around these issues.
>> If interested, contact me off Technet.
>>
>> Rudy Sedlak
>> RD Chemical Company
>>
>>
>>
>>
>>
>>
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