[roro]

hi all,
so I need to do a cool Corrosion rate experiment for my class, any ideas?
it need to be a safe experiment and all the equipment and materials need to be accessible to normal people like me
thank you very much

[Enthalpy]

I don't know if it's a "cool" experiment, but it would be useful to show to as many people as possible that aluminium alloys corrode, because the legend is extremely common and leads to design mistakes.

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One example I saw was a freshly machined rod (D=20mm, L=250mm) I had driven in a banal soil. After 1 or 2 days, the rod had a 1mm thick white crust that fell away easily. I believe the English term is "exfoliating corrosion". Quick and spectacular.

The soil was under leaf trees, nothing special, not conifers that make the soil acid.

The alloy was the uncommon AA 7049A (8% Zn), but I suppose the AA 7075 behaves identically, especially in condition T6 (and T651 or T652), not T73.

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Easy too: put aluminium wrap foil in water. Add (much) salt to the mean proportion in seawater. Despite this alloy is corrosion resistant, in about a weak it's punched. Graphical too. You can compare with sweet tap water.

You may also compare with and without a corrosion couple by adding a copper wire in the liquid, in contact with only one aluminium foil. I saw no difference.

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If you have old destroyed bunkers in the vicinity, or maybe other buildings, you can observe where the steel reinforcement rods were broken by corrosion. Good to know:
- After 70 years under the rain, here in temperate Europe, 15mm rods of banal steel are corroded but they lost little diameter;
- Where rainwater accumulate, including where bent rods were horizontal, the rods are broken by corrosion.
So steel has a useable resistance to corrosion, but it's a matter of proper design.

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I suggest that you make the trials for yourself before any demo in front of 100 people. Corrosion isn't very repeatable.