Oxidation in Al

Aluminum oxidizes very quickly, and rapidly forms an aluminum oxide coating that inhibits further oxidization, we are talking about a very very small percentage of the Al the that gets converted to Al2O3.

I assume that they are directly melting the Al instead of refining it, and this is why they are claiming the Al2O3 is causing issue, but this doesn't make a lot of sense to me if I am looking at the problem from a metallurgical viewpoint.

Refining Al is a very tricky thing, but even if they were refining, the very act of doing so reduces the Al2O3 to Al. The key is the Cryolite. They should be using it when they melt Al as part of their flux anyway, so it shouldn't matter if there is a very thin layer of oxidation on the Al.

There are also other concerns you might want to consider. If you shipped this, and the method of shipping exposed the Al to salt water spray for example, it could create a layer of crusty looking Al2O3 that would look like corrosion, but in reality would be a mixture of Al2O3 and dried salt. This might be the pictures they are sending you. In this case, your shipping insurance should cover this contingency, and if not you might want to look into doing so on your next shipment.

There is a very simple way to prevent most of the oxidation, without incurring the cost of wrapping in plastic. I am going to post a few examples, but unless I know how it's bundled, and how it's shipped, I cannot give you a really good solid answer. If yo provide that information I'll follow the thread and post here the changes.

First, you can remove any layer of Al2O3 by subjecting the Al to a solution of Sodium Hydroxide, or lye as it's commonly called. This will remove anodizing and the oxide layer on your Al. I am not sure how best to accomplish this on a large shipment of your type of material, but it does remove the oxidation.

If I were you I would ask if it's only the outside material of the bundle that is oxidized, rather than the entire bundle. If this is the case, then it's exposure to air, salt water spray, or something else that is causing the actual oxidation.

If it is only on the outside layer, you can spray the outside with soapy water, like a dish soap, and allow it to dry. This is simple to remove, and will not cause any problems during the smelting or refining process, it will simply burn off.

Another way, if you are shipping in large c-containers is to inject an inert gas into the container after loading. Or even better, covering in plastic drop clothes and injecting the inert gas under the plastic drop cloth before being loaded. The inert gas will not allow air to oxidize the Al. However, if there is water inside the radiators, you are still going to have the problem with oxidation. Matter of fact, water readily oxidizes Al. But this doesn't make a lot of sense to me either, most people put radiator fluid in their radiator, which is a oil based liquid. If this is what is in your radiators you cannot get out, I can't see how this would cause oxidation.

You could heat the radiators to evaporate off any water, but this also might cause extra oxidation if there is water, and not radiator fluid in your radiators. The other problem is that there might be some noxious or dangerous off gas in a process like this, that might be illegal where you live to produce and exhaust without the proper permit or license. I don't know enough about the laws that govern that type of thing in your country.

All these problems or issues however, would be the same for any load of radiators that your customer is purchasing. If they suggested wrapping them in plastic, it would seem this would only increase the problem because plastic would create a greenhouse affect. And in doing so water would evaporate, and then condense on the plastic and eventually be transferred back to the bundled/bailed radiators, probably making the situation much worse.

Has your customer given you any examples or pictures of what their other customers do to prevent the oxidation of the Al? If they process a lot of this type of material, I don't see how they wouldn't know the best way to ship it, but then again I don't understand either way it's an issue.

Scott

Like Noble says, I'd suspect exposure to the salt-water spray and surface oxidation (similar to surface rust on a car). I know there are products to apply to the aluminum to prevent this, just can't think of them right now. I know if you went to the Lets Talk Snow forum and asked, you'd get "snowed" with offers.
Let's Talk Snow.com Discussion Forums - Powered by vBulletin

Originally Posted by krdandu

Hey Scott,

Thanks for taking the time to explain. I did pick up quite a lot of information from your post. And yes the company is not refining the scrap they are melting it direct.
Well due to the strict regulations we make sure there isnt much of residual radiator left left in the radiators before bailing them. The water getting in there is usually
from rain ( storage and transport ) and shipping. Sometimes we get baled scrap direct from the supplier while other times we cut the attachments and then bale them
at our own facility. As of today we do not add any chemicals or blow them with air oranything like that.

Thanks

Cole,

I know some of them but they are limited by thier absorbtion capabilities.

Thanks

Okay so it sounds, if the radiators are in fact completely free of water, that wrapping them in plastic still might work, but I wouldn't do it. If you are just receiving and shipping the problem exists with the people shipping to you and you are just transferring the problem without knowing, or it's happening during the shipment to your customer, or your customer is using the excuse to beat you up over pricing. If you are knocking off the pipes and bailing them yourself, then I still can't imagine a situation where it is your fault.

Depending on how your bailer works, you could eject the bail on top of a plastic sheet, then wrap the sheet around the bale and melt/seat the plastic. There are also shrink plastic product sold for industrial scale use that will shrink to fit the bale once heat is supplied. I believe this is done under a heat lamp, or hot air induction. If you used this method with injecting inert gas they would never be able to blame any oxidation on you.

If I were you, I would look over your shipping insurance, specifically the part about damages during shipping and/or force majeure. If it was an act of nature, that could not be helped, it could be covered by force majeure, such as rain, salt spray, etc. If the shipping company didn't handle your material properly you might talk with them as well. Also, if I were you, I would notify your customer and explain to them this was totally unexpected, and that you will be turning it over to your insurance, so they might expect a call or an insurance inspector sometime in the future. In doing this, letting your customer know that there might be a nosey insurance inspector that will want to poke around their facilities, might just circumvent their current position, meaning they might just change their mind. Getting other entities involved that will be nosing around looking for the actual cause will make someone trying to pull a fast one on you, think twice.

Hope this helps.

Scott

here on the golf coast I have to keep my al rads inside or with in weeks I will loose 20% due to the salt humidity and rain.

If you are looking for a cheap desiccant, get you some cheap, dry coffee creamer, open a couple in a shipping container just before you close it up to ship.