Accelerated Weathering

There are different methods to accelerate rusting.

The first method is to bathe the object to be rusted into a water-based bleach and vinegar mixture.  I will not be using this method as it releases toxic chlorine gas.

The second method is slightly safer.  The instructions are to create a solution and spray that solution onto the object.  Given that the metal I would like to rust is mostly embedded in concrete, I will actually bathe the object in the solution.  Rather than creating a gas that can be inhaled, this solution creates an acid that remains liquid.

The instructions recommend chemical safe gloves and goggles and to work outdoors in a well ventilated area.

The object to be weathered is a concrete panel containing black iron shavings in its aggregate.

About the Solution

Combining vinegar and hydrogen peroxide creates Peracetic Acid which is highly corrosive.  It is also very dangerous and exposure can cause “irritation to the skin, eyes and respiratory system and higher or long-term exposure can cause permanent lung damage”.  Do not attempt creating this solution unless you hold a degree in chemistry.

Solution Ingredients [amended]

  • 16 oz white vinegar
  • 48 oz hydrogen peroxide
  • 1/2 cup salt [dissolved into water]
  • 8 oz warm water

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Procedure [amended]

  1. soak panel in vinegar.  remove. air dry.  repeat.
  2. after the panel has been “pickled”, place into a container.
  3. mix salt, water, and vinegar.
  4. carefully add hydrogen peroxide and give the container a swish.
  5. dump container and rinse panel.

Results

The mixture became cloudy and bubbles seemed to rise from the concrete.  The cloudiness seemed most opaque nearest the surface of the concrete panel.  Within 5 minutes I noticed some rust clouds coming from the rough side of the panel.  I used the container from a device from a previous experiment.  The tubes do not relate to this experiment.

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After about 15 minutes the cloudiness at the surface of the panel had dissipated.  The surface of the solution was frothy. I removed the  panel and rinsed it off.  Only places where the metal was most exposed were rusted.  I am now bathing the panel in water with the top 1/4 exposed to the air to serve as comparison.

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Immediately after rinsing.

In retrospect I think I should have left the panel in the paracetic acid solution for longer than I did.  This would have allowed it to more effectively seep into the pores of the concrete to reach all of the metal filings.  You can see in the image above where the exposed filings are quite dark.  Before being bathed in the paracetic acid these were mostly shiny.

Within 20 minutes of bathing the panel in water, I noticed the development of rust stains below the waterline.  They are small now but I will allow the panel to bathe for a few days to see if they spread.

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After 20 minutes of bathing.

After 24 hours of bathing.

After 24 hours of bathing.

After 48 hours of bathing in water, I observed that all exposed metal fragments had rusted completely.  Because the entire panel was bathed, the concrete is not stained.  Staining would necessitate water moving over the surface such as rain.

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After 48 hours of bathing in water.