Testing for Aluminium Oxide
Testing for Aluminium Oxide
(OP)
Hiya everyone,
I was just wondering if anybody knows how I can test for the presence of aluminium oxide? We have been shot blasting plastic with an aluminium oxide abrasive, so bits of this abrasive will be left on the surface of the plastic. We believe that we can remove this aluminium oxide using acetic acid (white vinegar). However, it is essential that there is no aluminium oxide left on the surface of the plastic. We therefore need some way to test for this.
Thanks
Kat
I was just wondering if anybody knows how I can test for the presence of aluminium oxide? We have been shot blasting plastic with an aluminium oxide abrasive, so bits of this abrasive will be left on the surface of the plastic. We believe that we can remove this aluminium oxide using acetic acid (white vinegar). However, it is essential that there is no aluminium oxide left on the surface of the plastic. We therefore need some way to test for this.
Thanks
Kat





RE: Testing for Aluminium Oxide
You could locate some particles embedded in the plastic and have a lab verify that it is Al2O3.
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
@arunmrao: We have tried about 15 abrasives on about 7 different plastics and aluminium oxide has been giving the best results.
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
If you can't tolerate the presence of aluminum oxide embedded in your surface then the best course of action is not to blast the surface with aluminum oxide.
You will NEVER be able to test all the aluminum oxide away.
Do you seriously think that it's realistic to test and confirm the absence of aluminum oxide on every square millimeter of every part?
You are starting down a path that will be excessively time consuming and expensive and also guaranteed to fail. You should rethink.
RE: Testing for Aluminium Oxide
Acetic acid will not remove aluminum oxide. Al2O3 is inert to acetic acid, so you aren't doing any better than soap and water would do (actually, soap and water may do better). Strong caustic (pH > 10) will dissolve Al2O3, but it may damage the palstic and will certianly damage any human tissue it comes into contact with (it is very dangerous), so a caustic wash may not be the best solution.
The best solution would be use a abrasive that is compatible with the product and processes
rp
RE: Testing for Aluminium Oxide
TTFN
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RE: Testing for Aluminium Oxide
Aluminum oxide splits and shatters in sandblasting. It does this even when sandblasting a soft medium because the particles impact one another. One of the shapes formed with regularity could be described as 'spears'. These aluminum oxide 'spears' penetrate and become embedded in tungsten carbide.
I would suspect that the spears formed by the breakdown of aluminum oxide grit would become deeply embedded in the plastic.
You may be able to find the report on this on the Internet. I remember seeing it because there was a lot of commotion about whether the aluminum oxide on the surface of tungsten carbide would interfere with brazing or not. Once we establish that the aluminum oxide penetrants occupied a miniscule percentage of the available bonding area I pretty well lost interest in the whole thing.
Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com
Good engineering starts with a Grainger Catalog.
RE: Testing for Aluminium Oxide
http://accuratus.com/alumox.html
Note that HF is EXTREMELY dangerous; use with caution.
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RE: Testing for Aluminium Oxide
It is possible that there could be a non-medical application where surface contamination wouldn't be as serious and the removal of aluminium oxide would be mainly for aesthetic purposes. In this case we would be able to try a few different chemicals (and different lengths of exposure etc) to remove the aluminium oxide. I can therefore try hydrofluoric and phosphoric acids as suggested. Thank you for your help.
RE: Testing for Aluminium Oxide
Again, I caution you about HF, since it's extremely toxic and hazardous, and not necessarily something you want to be handled by untrained personnel.
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RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
It is insidious as one drop on the skin especially the finger nails is quickly absorbed with resulting pain that feels like being pounded with a hammer. The affected area will take long medical and healing process.
It has to use in a fume hood. The use of an acid proof fume hood is very desirable.
It can not be worked in metal tanks.
Here two suppliers of plastic bleat media. Checkout both to see how it used, especially the Maxiblast Application
http://www.maxiblast.com/applications/
http://www.optiblast.com/products.asp
You could look at soda blasting, wet or dry.
http
You could also try corn cobs or walnut shells.
http:/
Or water ice blasting.
http://www.iceblast.net/faq00.htm
RE: Testing for Aluminium Oxide
@ Ron: Do you have any experience with ice blasting plastics. I have already been talking to some companies about dry ice blasting. The general feel I'm getting is that it probably isn't right for achieving a good surface finish on plastics. A couple of companies have said I can send samples for testing so I am currently waiting for some samples to be prepared so I can send them off. However, even if this works it looks as though it is going to cost far too much for us to start using this process. We would have to send samples off to one of these companies to blast for us, as we do not have the capabilies on-site.
@ Unclesid: I am going to buy some bicarbonate of soda at the weekend so I can test out soda blasting. With regards to ice blasting our on site air capabilities are not adequate so it would be very expensive for us. Thanks for the plastic blast media links and also the natural abrasives link, very helpful.
Kat
RE: Testing for Aluminium Oxide
The second link is to grit-o-cob blasting media
http://www.armex.com/
http://www.gritocob.com/product-list.aspx
If you are in the US and live near a Harbor Freight Store they carry the Armex material as we a soda blasting pots.
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
There are lots of very good polymer and plastics guys here that might come up with a simpler solution to your problem.
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RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
@IRStuff: The plastic cannot be made this way in the first place. It is complex engineering and must be cut and machined etc. There might be alternatives to shot blasting but the results that shot blasting has given are billiant. We therefore need some way to improve surface finish to this standard without using aluminium oxide, or alternatively we need to find a way to remove the al oxide afterwards. Maybe shot blasting with plastic blast media will work as our results for this are quite good. I'm sure we'll get there in the end.
RE: Testing for Aluminium Oxide
Plastics are ordinarily used where the geometry is complex enough to make machining prohibitively expensive, so you put the expense in a mold and make the plastic parts from the mold by means of a relatively primitive process...
Mike Halloran
Pembroke Pines, FL, USA
RE: Testing for Aluminium Oxide
Additionally, machining can entail using other tools that may allow you to get the surface properties you desire directly on the machine. It would seem to me to be cheaper to switch out a machine tool bit than to install the part on another machine, blast it, and then clean it, and the inspect it.
As I mentioned, if you tell everyone the entire problem, there may be another solution. By holding back you potentially deprive yourself of all the help you could be getting.
TTFN
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RE: Testing for Aluminium Oxide
It is not a cheap piece of equipment so we are trying to find the best way to make it, not the cheapest. We basically need some sort of way to remove machine marks and to deburr this plastic while not effecting tolerances. It also needs to not contaminate the part. For example, we could shot blast with a plastic media, but the results just aren't as good as they were with aluminium oxide.
RE: Testing for Aluminium Oxide
There are also many things to test like liquid blast with Al2O3 or others.
Continue blasting as you are and followup with a second blast media for a 2 stage process..
Change the angle of attack of the nozzle for your existing equipment.
If you can get access to a good microscope , preferably a metallurgical, you can probably be able to see the Al2O3 by varying the light.
http://www.airbrasive.net/
http://cmvblasting.com/index_ing.html
RE: Testing for Aluminium Oxide
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RE: Testing for Aluminium Oxide
We are shot blasting to remove machine marks and to deburr so that we have a smooth, even finish across the entire 1m diameter sample. We have achieved this surface finish with aluminium oxide and the customer is happy with this.
However, due to it being for a medical application we cannot use aluminium oxide. This is why I was asking about testing for aluminium oxide and removing aluminium oxide.
It appears as though there will still be traces of aluminium oxide whatever we do to the samples, so it doesn't look like we will be able to use aluminium oxide at all. The problem now is therefore different to the problem in my original post; we now need to find a different technique to give us the same surface finish. One possibility is therefore to blast with a different abrasive that wouldn't need to be removed before the part is used in the medical industry. Our main areas of focus are therefore currently dry ice blasting, soda blasting and blasting with acrylic media. If anybody has any tips for any of these 3 areas or any suggestions of alternative techniques that would be brilliant.
Has anyone used dry ice blasting or soda blasting for plastics?
RE: Testing for Aluminium Oxide
Have you consulted with others about using a different tool or cutting process that will not tool marks?
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RE: Testing for Aluminium Oxide
If not, small grooves and small ribs in the surface of a part, no matter how large, are certainly moldable. Even Teflon compression molding will give very good tolerances and surface finishes.
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
@Compositepro: Thanks, I will have a look into flame polishing.
@IRstuff: Yes I have consulted with others about using a different tool or cutting process and this is not going to happen. We have a good process in place and the customer is happy with this. We just need a way to improve the surface finish at the end of the process. We have had some good results after shot blasting with plastic media so it is possible that we will use this.
RE: Testing for Aluminium Oxide
Kat
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
Brush finishing is used for plastics
htt
Here is a different media you may want to look at. There is a lot of good information on other media.
http:
blasting-abrasives-briteshot-reg-#s
You may have to cut and paste the links.
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
Here is another approach that you may want to investigate if the quantities are high enough. The Covington Reciprol Laps go to 36" and it looks like it would not be a problem to enlarge the pan to accommodate your part. Very little additional weight is involved.
ht
http://www.lortone.com/laps.html
http://www.diamondpacific.com/moreproducts.html
I polished to mirror finish about 2,000 CS 1" dia disks. on our machine.
RE: Testing for Aluminium Oxide
RE: Testing for Aluminium Oxide
http://www
I have done this because over time the title of the thread was becoming less and less relevent and we now have a new problem. Thanks for help and advice everyone.