Prevention of Steel Oxidation: Cathodic or surface coating?

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Discussion Overview

The discussion centers on methods to prevent oxidation of steel, specifically in the context of protecting an etched Altoids tin placed outdoors. Participants explore various protective coatings and cathodic protection methods, considering factors such as environmental exposure and longevity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests using a rust-proof varnish coating, asking for recommendations on the most effective type or brand.
  • Another participant proposes that a surface coating should be combined with cathodic protection, noting that coatings generally outlast cathodes due to the latter's degradation over time.
  • It is mentioned that an exterior grade varnish is necessary to withstand sunlight, with yacht varnish being recommended as the best option.
  • A participant points out that for cathodic protection to be effective, the sacrificial anode must be in contact with the wetting part of the circuit, which would not occur if it is rolled up inside the tin.
  • Car wax or marine wax is suggested as an alternative protective measure, with a recommendation to inspect it annually for performance.

Areas of Agreement / Disagreement

Participants generally agree on the importance of using a surface coating to protect against rust, but there is no consensus on the effectiveness of cathodic protection in this specific scenario. Multiple viewpoints on the best protective method remain, with some advocating for coatings and others discussing cathodic protection.

Contextual Notes

Participants express uncertainty about the longevity and effectiveness of various coatings and cathodic protection methods under specific environmental conditions, such as humidity and exposure to sunlight.

Who May Find This Useful

This discussion may be useful for individuals interested in metal preservation, outdoor art installations, or those seeking methods to protect steel items from oxidation in humid environments.

wil3
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Hello- I recently etched an Altoids tin. I would like to leave the etched tin in an outdoor location as a memorial to something. The etching includes text, and I am worried about oxidation of the steel ruining the tin quickly. I would ideally like for this to last several years (as long as possible)

What is the best way to protect the item from rusting? Should I just use a rust-proof varnish coating? If so, what is the most effective and long-lasting type/brand?

Would a better option be to attempt cathodic protection? I could easily roll up a lot of Magnesium ribbon and place it within the tin- how long will this last?

This is going to be left on a rooftop in Florida, so it will be exposed to humidity, sun, and rain, but it will not be submerged. Does this make cathodic protection ineffective?

Thank you.
 
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If it is going to be in a relatively low traffic area, coat it. Even with cathodic protection, you would still want to combine it with a surface coating. Assuming it's not damaged or worn away, a coating is always going to outlast a cathode; that's the nature of cathodes, they degrade to work, and thus, will eventually run out.

I would say the most practical thing to do is to buy a can of varnish/clearcoat/PU and just hit it with several layers. Should do the job.
 
Use an exterior grade varnish or sunlight will degrade it within a year. Yacht varnish is probably best.

For cathodic protection to work you need to include the sacrificial anode in the wetting part of the circuit. This will not happen if it is rolled up inside the tin.
 
Car (automobile) wax, or the marine equivalent, would probably work. Then perhaps spray it with silicone spray. You might need to inspect it annually to ensure it's performance.

I used to do iron work on metal buildings. One of the old timers told me that car wax would extend the life of the sheet metal, but people rarely did that.
 
Car (automobile) wax, or the marine equivalent, would probably work.

Nice one!
 

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