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Titanium Machining using coolants containing chlorine

countryboy1966

Hot Rolled
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Jan 10, 2009
Location
Thompson, Ohio
I'm preparing to machine titanium for a product of mine and while studying best practices for machining titanium, I stumbled upon an issue with machining titanium using coolants containing chlorine. In some cases it was found to cause stress corrosion cracking in some tests.

Titanium: A Technical Guide, 2nd Edition - Matthew J. Donachie - Google Books

With that said, I'm running blasocut 2000 Universal and it Swisslube Tech Sales says it should be fine becuase of the low chlorine parafin base similar to their BC940 that is better suited for Titanium.

The question I have is anyone else that runs Blasocut 2000 Universal ever have issues with titanium related to this topic? I'm not making mission critical or even areospace parts.

I will be doing very limited titanium parts so I'm hoping to get by with the coolant I'm using for the time being and if I go to do a change out down the road, I'll assess if I should make a change to a more suitable coolant at that time.

Any help is appreciated.
 
This does not specifically apply to your coolant question, but is another thing to consider. The shop I retired from had to have the chlorine level of the water used to mix coolant tested to ensure that it was below some level required for the parts we were making.
 
..The shop I retired from had to have the chlorine level of the water used to mix coolant tested to ensure that it was below some level required for the parts we were making.
When I was in Seattle, the company that disposed of my used coolant would test it before taking it. They had 2 different tests, one was a simple screen and the other was a GCMS. They always said it had too much chlorine and had to be sent to a special facility. I would tell them to do the GCMS- what they were seeing was the chlorine in the water. After the more detailed test, they would agree and take it to the normal disposal location. It was the difference between ~.50/gal and ~5.00/gal to get rid of, and it took the mass spec to show that it wasn't chlorinated paraffins they were seeing.

We put in a heat treat plant. We had a Lindberg pit furnace for aluminum. Next to it was the quench tank, when we'd heat it up you could stand next to it and the chlorine smell was like you were in an indoor swimming pool.

Some municipal water has a lot of chlorine.
 
I'm preparing to machine titanium for a product of mine and while studying best practices for machining titanium, I stumbled upon an issue with machining titanium using coolants containing chlorine. In some cases it was found to cause stress corrosion cracking in some tests.

Titanium: A Technical Guide, 2nd Edition - Matthew J. Donachie - Google Books

With that said, I'm running blasocut 2000 Universal and it Swisslube Tech Sales says it should be fine becuase of the low chlorine parafin base similar to their BC940 that is better suited for Titanium.

The question I have is anyone else that runs Blasocut 2000 Universal ever have issues with titanium related to this topic? I'm not making mission critical or even areospace parts.

I will be doing very limited titanium parts so I'm hoping to get by with the coolant I'm using for the time being and if I go to do a change out down the road, I'll assess if I should make a change to a more suitable coolant at that time.

Any help is appreciated.

Generally in aerospace and defense applications we/they get rather paranoid about the presence of chlorine/chloride ions. Chlorides or Cl- ions are what is called (extremely/very electronegative, which means they have a very high charge density and the size of the choline/chloride ion is extremely small) ... So that means it can get into metals almost interstitially and stay fairly trapped almost indefinitely especially if there are porous surfaces. chloride ions are the principal mechanism for starting corrosion pitting (in the presence of water) which dissociates or partially dissolves the (host metal) into solution which then causes a more acidic environment in the corrosion pit. This is an auto-catalytic process and there is a run away effect (all be it slowly) that as the pitting progresses more and more acids in the pit are produced as more and more "metal" being dissolved (by the acids as it were) creates an even more acidic solution which dissolves/corrodes more metal (and so on and so on). BUT this is all initiated by the presence of very small amounts of chloride ions and moisture and water. So in processing its usually stated that intensive washing is required and a very light finishing cut (I assume without cutting fluid/chlorinated compound) is required to remove a layer of metal that would probably contain chlorides.

Beyond that there is a paranoia that any other materials that chemically might contain chlorine in them might be a problem. A lot of this paranoia comes from association (like your article and citation is saying)from use of hot salt type process (but that is a pretty extreme process compared to the use of chlorinated compounds used in industry). Stress corrosion and high temperature components that have been exposed to chlorides have had compromised service lives / failures (found in the past)... But a lot of these things are anecdotal and the experimental design for testing some of these things is not so great/perfect as accelerated aging tests are not indicative of field conditions over longer periods of time. So it's easier for spec'ing defense and aerospace based processes to take these precautions so that chlorinated compounds don't start to "Creep" in to the process on their own. If they are singled out or "Banned" then they can't creep in to important processes over a period of years.



To OP in your case I'm sure you will be fine unless you have a component that experiences severe stresses in aggressive environments or is extremely porous. If you are also "Paranoid" you can put your cleaned parts into a tank of de-ionized water and leave it for a day and then measure the conductivity of the water. measure the changes. If you notice the conductivity of the water to increase then you probably have various ions floating in solution, that may indicate that you need successive washing with de-ionized water. (if you have a conductivity meter you can plot that out, and there are also special meters/detectors to plot out the concentration of chloride ions in solution... Not everybody has one of those (lol)).

I'm sure you will be fine. If "Blasocut2000" had excessive amounts of deleterious chlorine compounds then it would have played havoc with other metals too and we would have heard about that.

Also bear in mind that chlorinated hydrocarbons are different from aqueous base solutions containing chloride ions. The US Navy did a bunch of research on chlorinated hydrocarbons for use of cleaning/degreasing potentially causing long term destabilization of aluminum but really required sticking aluminum components into baths of pure chlorinated solvents and then putting the aluminum components into pure salt water to determine a slight difference. Although titanium alloys are very different the concentration of Chlorinated compounds in "Blasocut2000" is probably fairly minuscule and then how many of those compounds actually have chloride based salts ( I bet virtually zero/will check it out) I.e. actually have the ability to go into solution? ... As "Chlorine" and "Chlorinated" is very different from "Chlorides" that are aqueous based and DO indeed cause corrosion i.e. able to get into solution and cause havoc/corrosion... So I think there is just a bit of paranoia with the pre-fix Chlor... And a lot of aerospace Engineers are not necessarily chemists or "experts" in corrosion mechanisms :-) Chlor-something just scares them :-) And to be honest for mission critical components justifiably so IMO always err on the side of caution as the precise effects and mechanisms haven't been nailed down yet/completely.

What is the titanium "stock" or casting you are cutting do you know its composition/ alloy?

@OP Thanks for the posted link, that reference for "Titanium" look excellent... I might buy that one! Cheers

Personally I think stearates and Polyethylene glycol and glycerol and other glycols are more of a concern than chlorinated hydrocarbons as far as potential long term corrosion problems and even CRC softseal ! Stresses the importance of multi stage part washing and degreasing for mission critical parts.
 








 
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