Why does my kiln corrode so quickly?

Corrosion on a kiln is perfectly normal... mostly because it is a kiln! Hot-to-cold-to-hot environments, plus all the water vapor, not to mention sulfur, fluorine, carbon, etc. coming out of the clay all work to create a very corrosive environment for metal.

Corrosion In Different Materials

  1. Corrosion to untreated steel will happen overnight, even when it is not part of a kiln.
  2. Corrosion to galvanized or aluminized steel- like chimney flashing, or like your kiln's stand, won't happen as quickly, but it will happen.
  3. Stainless steel, like the kiln casing, is better- it can take many years to rust it, but it will blacken or pockmark rather quickly near the heat.
  4. On a kiln, everything discolors and corrodes pretty quickly. How soon this happens will depend entirely on several factors.
  5. The #1 reason why kilns corrode is for lack of down-draft ventilation. We highly recommend installing a down-draft type vent (the Vent-Sure) to get the corrosive fumes out of the kiln. A room vent and/or a hood vent do not extract the corrosive fumes from the kiln itself.
  6. The #2 reason why a kiln rusts is a lack of ventilation in the kiln room. If the room gets hotter when you fire, then there is a build-up of moisture-rich corrosive air surrounding the kiln.

L&L's Kiln Vent

Using a downdraft kiln vent like L&L's Vent-Sure will minimize fumes and water vapor coming in contact with your kiln's outside. Using a good room venting system designed and sized by an HVAC engineer will keep any other corrosion to a minimum.


  1. If you are making your own clay you may have a higher concentration of the minerals that cause acids to be created in the hot moist environment of the kiln.
  2. If you are seeing excess corrosion and you have a down-draft vent that is working properly then the next area to examine is the clay that you use. Check with your clay supplier.


  1. If the kiln is kept outside (some people in warm relatively dry climates do this) remember that dew can form on the kiln case in the morning and this can lead to corrosion (even on stainless steel).
  2. Also, people who live near the ocean can experience higher than normal rates of corrosion from the salt in the air. The best protection for this is the keep a kiln inside.

Guidelines for putting a kiln outside

You shouldn't keep your kiln anywhere that you wouldn't keep a $5000 computer. You may be able to get away with it in Arizona, but I would not try it in Maryland. Here's a list of reasons it should not be kept outdoors:

  1. Weather is unpredictable and impossible to stay 100% out of unless you have a fully enclosed space. Blowing snow and rain can get all the way under almost any overhang. High winds could easily blow debris or patio furniture that damages your kiln.
  2. You would have an increased fire risk because the wind could blow something flammable against your hot kiln. It's not just the 10 hours of firing that are an issue; it's also the 12-16 hours of cooling. Can you sleep well knowing there is a 2000-degree kiln on your patio that could cause a fire if a stick blows up to it?
  3. Rain, snow, high humidity, fog, morning dew, etc- any form of moisture- can make a mess of the controller. Even if it doesn't cause permanent damage, it can cause the controller to malfunction until it dries out.
  4. Moisture will drastically increase the corrosion rate of all the metal parts on the kiln, especially electrical connections. This will drive up your maintenance costs, result in more mis-firings, and reduce the overall lifespan of the kiln.
  5. If the bricks get wet, you'll need to dry them out before firing, which wastes electricity and your time. Repeated wetting will reduce the lifespan of the bricks.
  6. Critters and insects can be a real problem with an outdoor kiln. At the very least, your control box will get a lot of spiderwebs, but you could end up with rodents chewing on or even nesting in the kiln. I've seen several mouse nests inside kilns. I'd hate to see what a raccoon can do to a kiln.

Overall, keeping it in a simple shed will likely cost you less in time and money. Plus, if you needed to fire in really cold temps, you could actually heat the shed. For me, the peace of mind that comes with keeping it protected would be more than worth the cost of the shed. Kilns aren't cheap, so spending a little to protect it makes sense.