Hello,
I am studying the dry sliding behaviour of some materials. I have to clean some small metallic parts that will be in contact. The contact zone is a circular plane rough surface. After they are fabricated, I have to be very careful not to damage the surfaces.
At the moment, I am using this procedure :
- acetone bath for 10 mn
- ultrasounds with ethanol for 15 mn at 40°C
- acetone bath again for 10 mn
- rinse with ethanol
- dry with a hairdryer
Is it possible to store the parts in a way that totally avoid the formation of oxyde layers ?
Thanks a lot for your advice.
Rémi
You may use the vacuum or inert-gas blanket in your setup (tribometer) to avoid the formation of oxyde layers on metals.
Good Morning Remi,
I don’t believe we have enough information to make an experienced-based recommendation.
We need to know at least two pieces of information, and possibly three: (1) what are the soil materials on the metal surfaces and how did they get there, and (2) to what extent they must be cleaned. It would be also helpful to know of what metal they are made.
Peter Blau writes well of the action of oxidation. To extend his ideas, if your metals are either aluminum or possibly titanium, the cleaning / transport / storage must all be done in an oxygen-free environment. And more so, the cleaning may well have to be done with de-aerated water.
I look forward to hearing from you.
John Durkee
Hello everyone,
firstly thanks a lot for your answers and advice.
the materials I have to study are Aluminium 7075 and Titanium TA6V. I am studying sliding in bolted joints so the loads are quite high (max 30 kN). The clamped parts of the bolted joints are made of these two metals. I retained two configurations of contact : al/al and ti/ti. I do not have to be very strict about the formation of oxyde layers, but I would like my tests to be as "reproductible" as possible, so at least I would like to have approximatively the same oxyde thickness on all the samples. I do not have any mean to clean my samples in vacuum neither to store them in vacuum, neither in an oxygen free environment.. The only thing I could do is to use deaerated water, sodium hydroxyde and a dessicator as suggested.
Thanks again. Best regards.
Rémi
Hi Remi,
What's the reason for cleaning the parts; what is the soil on them and just how clean do they have to be?
John
ps: you probably already knew about this: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760014468.pdf
Hello John,
the reason for cleaning the parts is to be as close as possible to dry sliding conditions. These conditions should be encountered in space. As I can't do any test in vacuum for the moment, I wanted at least to have dry sliding. In reality, the parts are assembled in a clean environment but not in vacuum. So I think even in reality there still is an oxyde layer.
By soil, do you mean grease or things like that ? There is some oil from machining, some finger traces, etc. There are not very dirty.
Yes I already know the document you mentionned. Thanks.
Hope I answered your questions...
Rémi
Good Evening, Remi,
Well, I think this is the best advice I can provide.....
First, if the soils are only hydrocarbon-based oils, we could use either aqueous or solvent technology. But since aqueous technology involves a combination of surfactants and applied mechanical force, I don’t think we want to take a chance on ruining the surface character of your materials by basing our cleaning approach on use of force.
So, I propose we use a suitable solvent to dissolve the hydrocarbon-based oils.
● If the oils are truly hydrocarbon based, I would use a simple hydrocarbon solvent such as heptane or pentane if we need rapid drying. Acetone, alcohols, and ethers are not useful solvents for straight hydrocarbons.
● BUT, if the oils are synthetic, such as those which contain ester groups, then the use of an oxygenated solvent (such as acetone or ethanol) is absolutely required for the best cleaning. Remember, “like dissolves like?”
As to rinsing and drying, any of the above options would rapidly evaporate and produce dry surfaces. Rinsing, by dilution with fresh solvent, is problematic. Since I don’t know how clean the parts have to be, I don’t know how many dilution volumes of solvent are necessary to dilute the oil in the solvent film remaining on the parts. As a guess, I would dilute 10 / 1 fresh solvent / oil-bearing retained film.
Finally, how do we know how clean are the parts after cleaning? We don’t; that involves a cleaning test. Again, not knowing how clean the surfaces have to be of oil, I would suggest a non-invasive approach of using “Black Light” and looking for fluorescence – the more fluorescence is seen are the surfaces more oily.
Hope some this makes sense, and helps!
Good luck
John Durkee
Hello John,
thanks a lot for your very complete answer. Sorry I have not all the details you asked for about the soil, etc. I will have to clear all that. And I will try to run control tests for cleanliness as you suggest.
Thanks again.
I wish you a good continuation in your work.
Rémi
Good evening, everyone. In previous answers of collegues the methods of cleaning by solvents have been assumed thoroughly. For the general picture I should like to add the cleaning of surfaces by plasma treatment.
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