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Prevention of Steel Oxidation: Cathodic or surface coating?

  1. May 16, 2010 #1
    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.
  2. jcsd
  3. May 21, 2010 #2
    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.
  4. May 21, 2010 #3
    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.
  5. May 21, 2010 #4


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    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.
  6. May 22, 2010 #5
    Nice one!
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