Will rust travel opposite of gravity?

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Discussion Overview

The discussion centers around the behavior of rust in relation to gravity and its movement through concrete when galvanized nails are used to secure lumber. Participants explore the mechanisms that may influence rust migration, including moisture, capillary action, and diffusion, while debating the implications of these processes on the visibility of rust stains.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant argues that if nails are set below the concrete surface, rust will not travel up to the visible deck, suggesting that it would follow the path of least resistance.
  • Another participant introduces the concept of capillary action as a potential factor influencing rust movement, implying that moisture could affect the behavior of rust.
  • A later reply adds diffusion to the discussion, indicating that rust could travel in all directions, including upwards.
  • One participant humorously notes that rust, like life, will find a way, suggesting an inevitability to rust stains.
  • Another participant provides a detailed explanation of how carbonation and chloride diffusion from the surface can lead to rust formation, asserting that rust is ultimately inevitable due to these processes.

Areas of Agreement / Disagreement

Participants express differing views on whether rust can travel upwards through concrete. While some suggest that it may not, others argue that processes like capillary action and diffusion could facilitate upward movement, indicating that the discussion remains unresolved.

Contextual Notes

Limitations include assumptions about the behavior of rust in concrete, the influence of moisture, and the specific conditions under which rust may form or travel. The discussion does not resolve the complexities of these interactions.

Gary Weller
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TL;DR
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.
 
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I'm not really sure what you're talking about but with moisture involved, you might look up "capillary action"
 
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phinds said:
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.
 
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Add diffusion to processes that will make the rust travel up (actually in all directions, "up" included).
 
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Like the quip about, 'Life will find a way', so will rust stains...
 
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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.
 
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