We want to do a process in which the NaCl may be entrapped in Aluminum after solidification. I am concerned about the possible corrosion as a result of salt presence in bulk.
If you can ensure that NO water is present in the salt or air or on the aluminum, you should be fine. If there is any...expect corrosion. I've seen salt water eat through an aluminum frying pan in a few months. If at all possible, the safest bet is to line it with a plastic.
Agreed, but entrapped salt is quetion mark? consider if there are voids
To answer such questions, I think you have to tell us about the nature of the Al surface itself-because the Al2O3 layer on the Al surface is the key of your inquiry. Porous and soft layer coud be enhance the diffusion of ions from NaCl side and so on...
Of course, NaCl is corrosive salt in presence of water, which is difficult to avoid.
Also, Al alloy composition and surface finishing is important to control the corrosion process. In dry condition you may decrease the corrosion but you can not stop because sodium ion hold water tightly.
Mohammad, it is worthy to say that there is no humidity in surroundings. So, the threat of H+ and OH- iones is not an issue of concern. In you opinion, the corrosion occurs in this conditions?
Al itself is active. Al & its alloys have excellent corrosion resistance is predominantly due to the presence of passive film, which is thin, continuous, nonporous, insoluble and self-healing if broken in the presence of oxygen, on their surfaces. however, this film can breakdown and result in localised corrosion in certain environments, especially when exposed to a solution containing chloride and dissolved oxygen. As you might have known, wet corrosion will not occur if no electrolyte (salt in water e.g.) is present. So the critical issue is how you keep the container or box completely dry because moisture will always present due to condensation if the Al & NaCl are kept in a normal container or box.
Al generally forms a passive film i.e. Al2O3 on the surface. But in the presence of chloride environment the oxide film losses their stability. And localized corrosion takes place i.e. corroding at a very energy area where it is thermodynamically unstable. Generally pitting corrosion takes place.
If interested do experimentally by taking a small thin sheet aluminium and put it in salt water of high concentration. Then keep it for 5- 6 months. Then remove it and check in microscope . You will find fine holes on surface i.e. pitting corrosion.
But the corrosion can take time depending on concentration, temperature, etc
To avoid this U can anodised, coating, fine surface without any high energy area like pores, cracks, impurities, or use other metal.
I hope this might help you..
Long term you would end up with a box full of aluminum riddled with corrosion. Short term protection would be to treat the aluminum with a conversion coating, longer protection would be to anodize it. Type II anodize would be good, but Type III (Hard Anodize) would be much better. But again long term, corrosion would occur.
Since it is dry box reaction will not happen. If moisture present certainly Cl- will corrode aluminum and the reaction is temperature dependent (
K = (KT/h) e∆S/R .e-∆H/RT)you can slow down the corrosion by keeping it @ low temperature.
Theoretically, nothing would happen. That is, corrosion is a re-dox reaction and without anything that can be reduced you cannot have oxidation. However, in practice this is not so easy to achieve (as the comments above indicate). Considerable work has been done on electroplating of Al in low temperature molten salt baths containing chlorides (to remove the oxide film). I believe that they have figured out how to do this without significant
corrosion. So, I would look at that literature to see how they do it.
Practical observation predicts that this does not occur, but it is possible, after a long period of time, for the action of the halides present to produce corrosion-prone spots.
- Badges
- Science topic
- Similar topics
- Computer Communications (Networks)
- Simulators