Will rust travel opposite of gravity?

[Gary Weller]

TL;DR Summary

There is an iron nail in the middle of a concrete slab. As it rusts, will this rust stain travel with gravity, or could it possibly travel up toward the sky?

I work in the swimming pool industry. We often lock lumber into concrete by hammering hot galvanized nails half way into the lumber for the concrete to grab a hold of. In an "argument" with my boss, I told him if we set the nails at least an inch below the top of the concrete, the rust will not travel up to the visible deck. He argues that it can. I assume this "liquid rust" (if you will) would follow the path of least resistance, like most liquids do. I just can't imagine the path of least resistance would be up when there are just as many gaps beneath the nail as above. Just looking for somebody to back me or correct me.

 

[phinds]

I'm not really sure what you're talking about but with moisture involved, you might look up "capillary action"

 

[Gary Weller]

I'm not really sure what you're talking about but with moisture involved, you might look up "capillary action"

Actually, this was the perfect reply. It would absolutely prove me wrong. Thank you.

 

[Borek]

Add diffusion to processes that will make the rust travel up (actually in all directions, "up" included).

 

[Nik_2213]

Like the quip about, 'Life will find a way', so will rust stains...

 

[chemisttree]

Everything bad for concrete and embedded iron would come from the top of the deck. Iron is normally passivated against rust by concrete's high pH but atmospheric CO2 neutralizes it. A “carbonation front” WILL move from the outer surface towards the interior until it reaches the iron and then rust will begin to form. It’s like a fuse.
The pool is also kept in a state to inhibit bacterial and algal growth using chlorine either added or generated in situ. This means that chloride will also be available on the surface and will diffuse toward the iron. Soluble salts present on pool water will infiltrate the concrete pores and will potentially cause surface spalling and erosion when they dry and expand (salt corrosion).
Rust is inevitable.