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
- Corrosion to untreated steel will happen overnight, even when it is not part of a kiln.
- Corrosion to galvanized or aluminized steel- like chimney flashing, or like your kiln's stand, won't happen as quickly, but it will happen.
- 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.
- On a kiln, everything discolors and corrodes pretty quickly. How soon this happens will depend entirely on several factors.
- 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.
- 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.
- 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.
- 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.
- 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).
- 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.