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Subject:
From:
Ken Bloomquist <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ken Bloomquist <[log in to unmask]>
Date:
Mon, 30 Mar 2009 06:53:23 -0800
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Hi Inge,

I'm curious how you are going to prove that your part is "clean" once all
your cleaning is done. If the oils are tenacious and imbedded in the surface
of the titanium how do you plan to test for them?

KennyB

-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]] 
Sent: Monday, March 30, 2009 7:40 AM
To: [log in to unmask]
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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