Aluminum oxide to polish brass?

[rivertrash]

Does anyone have any experience using ultra fine aluminum oxide powder with your walnut shell or corn cob media? Just wondering if there was a chance it could damage my dies. Some of the RCBS media I bought came with a "white oxide" powder that really makes the brass shine and I suspect it is aluminum oxide. Any thoughts?

[Unclenick]

It could be, but aluminum oxide comes in forms other than the familiar lapping compounds, such as the porous bloom of oxidizing aluminum metal. If it is aluminum oxide, it will be extremely fine, so that its a true polish and not a lapping abrasive. Polishes tend to smear surfaces rather than cut them. It might also be something else like zinc oxide.

I would try something known to be a soft polish, like a tablespoon of white automotive buffing compound. That stuff doesn't even scratch paint. White diatomaceous earth from the garden supply works. It's what is used in toothpaste.

[Nosab]

I bought some from Harbor Freight thinking the same thing. Once I opened the jug and ran some through my hands I noticed a couple of things. One is that it is not that soft. Two it is kind of sharp/jagged. Three the size of each and what it might do to the flash hole. I decided against using it since walnut takes long enough and it is round-ish. I didn't want to remove metal I wanted to remove grime, so I needed something softer than the metal but harder than the grime. I have tried the auto polish and did that for a couple of years, I didn't like some of the media always sticking together no matter how long I ran it. I have found that cheap dryer sheets (unused) work the best since the are tallow and fragrance. I slice one into thirds and throw it in with each batch. The brass comes out clean and shiny and I have found that the media lasts so much longer and I have no dust, I mean zero. I never got that with auto polish even when it tried NU Finish.

[Roadkill2228]

I know there's no reason this should ever happen but I sure wouldn't want any chance of that aluminum oxide entering my rifle in any way (and that includes if residual amounts of it are trapped inside the cartridge to be sent down the barrel upon firing)...aluminum oxide is the same thing as carborundum, 9/10 on moh's hardness scale (diamond is 10), used in many heavy cutting industrial applications where diamond would be too expensive. definitely harder than the metal in our rifles and definitely unnecessarily hard for use on something so soft as brass. there are more appropriate choices.

[flashhole]

I've used Alumina (Aluminum Oxide Al2O3) in ceramic sheet form to sharpen knives. Makes for a great edge on carbon steel. Point being it was a lot harder than the steel blade. I would not recommend using it on brass. Not because it won't polish it, it likely will but I wouldn't want the material being blown down the bore. Residual material inside the brass may cause a problem.

[Road_Clam]

I've tried several different additives in my corn Cobb and for me Mothers MAG polish in the squeeze bottle works the best. My brass comes out looking like new. Even older tarnished mud brass shines up pretty decent.

[Mobuck]

I don't want abrasive powder embedded in my brass cases.

[DadsMod12]

I wouldn't use aluminum oxide to polish my brass. I cut and polish stones with aluminum oxide and the finer grades are expensive. The last time I checked Linde made 3 grades of polish: Linde A is a 0.3 micron polish, Linde B is 0.05 micron polish, and Linde C is a 1 micron polish. Big time overkill for polishing brass.

I've had good luck with a walnut/corncob mix with a little Nu Finnish in it.

[briandg]

You can find jewellers rouge on a m axon and other places. Forget AlO. Rouge is as fine as calcium. Nix with either cob or nut.

You could also look at diatomacious earth, but that's a really light abrasive

[rodfac]

Seems to me that any residual left in or on the brass will find its way into your dies and press, eventually, a source of problems for sure. Rod

[F. Guffey]

I use tumbling media and nothing. When it comes to something between the case and die; same thing, I want nothing between the die and case but air and lube. When it comes to the chamber I use the same philosophy. I want nothing between the case and chamber but air, I prefer clean air. And when my cases stretch I want to know where they stretched.

When it comes to adding ‘bling’ to cases I can do that also. I can make my cases so slick nothing sticks them except case lube. If 70% contact is good; 100% contact is better.

F. Guffey

[Tony Z]

If you really want shiny, get some Dillon case polish to charge your tumbling media. Cheap and works well.

I would not use aluminum oxide or silicon carbide powders, even in the finest grades-stick with time tested items, by equipment suppliers, if you really want shiny. I'm not quite as minimalist as Fred, by tumbling part on part, but I'm not far from that, by part on part, with some media.

[TriggR]

Well I had to try the aluminum oxide I mixed a couple of handfuls in with my Walnut shells and I feel it worked great.
I never take anything out of a dry media and run them through my dies they are gritty with the aluminum oxide, I run them through the Sonic Cleaner again with vinegar they come out just as smooth and nice as any media. You may not need to do this on all the brass but if you have some that is really bad this works really good, it also cleans the flash holes out really nice. I'm not one who needs to be in a hurry, needs to clean them and load them immediately I might run them two or three times through the Sonic (5-10 min) in between and after any dry media.

[HiBC]

A 2016 post !
You can do things your way. I have my own priorities.
I have done a lot of polishing work using brass for a lap. The grit embeds in the brass and becomes a cutter tooth.
Its true the brass is soft,but brass with embedded abrasive grit can cut the hardest steel.
Perhaps you could try putting some of your aluminum oxide powder mixed with a little resizing lube on the side of a hard knife blade. Rub it for 20 or 30 seconds with a piece of cartridge brass. See what you get.
Now imagine the effect of a few thousand rounds through your sizing die.
Embedded grit does not rinse off.

For myself (you do you) I do not care one bit about bright,shiny brass . I do care very much about clean brass. I do not want embedded range grit.
Brass cleaning has advanced some lately. I'm behind the curve. Folks are using stainless pins and lemon shine...And they are happy! Brass looks like new.
I'm still using walnut lizard litter...plain,or the green Lyman media,or corncob.
I use it plain or with a touch of mineral spirits.

Clean is necessary. Clean may not look shiny. Shiny can be gritty. Gritty is not clean. Shiny is not (IMO) necessary.

[Nick_C_S]

I sure wouldn't want any chance of that aluminum oxide entering my rifle in any way

I'm leaning this way ^^.

In a previous life, I worked with Aluminum Oxide as ceramic parts (and Beryllium Oxide too, but that's a whole 'nuther story) for radar jamming equipment. I am familiar with the substance in its many forms. And yes, the stuff is really hard (and brittle) and wouldn't want it near my guns.

Vibra-tumbling with corn cob has always made my brass plenty shiny. Everybody has different situations, but this sounds a bit like a solution in search of a problem.