Why galvanised item always protected from rust?

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Discussion Overview

The discussion centers around the protective properties of galvanized items against rust, particularly focusing on the mechanisms of galvanization and the role of zinc as a protective layer. Participants explore the theoretical and chemical aspects of galvanization, questioning how items remain protected even if the zinc layer is compromised.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant cites a textbook claim that galvanized items remain protected from rust even after the zinc layer is broken, prompting questions about the underlying reasons.
  • Another participant suggests looking up galvanization for more information, indicating a reliance on external sources for clarification.
  • A participant provides a summary from Wikipedia, stating that galvanization protects through a corrosion-resistant zinc coating and that zinc acts as a sacrificial anode, which raises further questions about the meaning of these terms.
  • Some participants express dissatisfaction with the explanations found in sources like Wikipedia, arguing that they lack depth in the physics and chemistry involved, and propose a more detailed inquiry into why zinc is used instead of other metals like copper.
  • There is a metaphorical comparison of research to tracing a thread from a spider web, emphasizing the complexity and interconnectedness of the topics related to galvanization.

Areas of Agreement / Disagreement

Participants generally agree that galvanization provides protection against rust, but there is no consensus on the clarity of existing explanations or the specific mechanisms involved. Multiple viewpoints and questions remain unresolved.

Contextual Notes

Participants express uncertainty regarding the adequacy of common descriptions of galvanization, highlighting a potential gap in understanding the physics and chemistry behind the process. There are also unresolved questions about the choice of zinc as a protective metal.

kingskj
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In my science textbook it is written that even after the zinc layer in galvanised articles is broken, the items remain invincible to rust.

Why is it like that? How come it could not rust after losing the protective layer?
 
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Have you looked up 'galvanization' from any source, like a book or the internet?
 
Yeah
 
http://en.wikipedia.org/wiki/Galvanization

Galvanizing protects in two ways:

-it forms a coating of corrosion-resistant zinc which prevents corrosive substances from reaching the more delicate metal
-the zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc.
 
kingskj said:
Yeah

what'd it say , wiseguy ?
 
aroc91 said:
http://en.wikipedia.org/wiki/Galvanization

Galvanizing protects in two ways:

-it forms a coating of corrosion-resistant zinc which prevents corrosive substances from reaching the more delicate metal
-the zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc.

I am with the OP on this one.
Galvanization works but how.

Protective, you mean like paint?
Sacrificial anode - what does that mean?

Most descriptions are of the type given by the Wiki, which with a lot of words, says little, leaving out the physics and chemical description, with the reader still not any wiser.

maybe a better approach is to ask and answer
So why zinc?
Why not copper?
 
256bits said:
I am with the OP on this one.
Galvanization works but how.

Protective, you mean like paint?
Sacrificial anode - what does that mean?

Most descriptions are of the type given by the Wiki, which with a lot of words, says little, leaving out the physics and chemical description, with the reader still not any wiser.

maybe a better approach is to ask and answer
So why zinc?
Why not copper?

Research is like tracing a thread from a spider web: you start off wanting to know how galvanization works, and this leads to a discussion of galvanic action, then to anodes and cathodes, then to ...

You've got to start somewhere, but this doesn't mean necessarily that you can make only one stop along this path and gather all of the information to answer your question.
 

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