Ask the Experts Metals

	Zbigniew Zurecki Research Associate

The green color that you see on stainless steel parts is chromium oxide (Cr2O3). It forms when there is too much oxygen and/or moisture in the furnace atmosphere, which is usually caused by a water leak, poor atmosphere tightness, or overly low flow rates of atmosphere gas. A dark green-brown color indicates significant levels of free oxygen inside furnace originated by a large air leakage.

In addition to the traditional steel and copper test, some companies run a piece of stainless through the furnace to check for high moisture and oxygen levels. A better and more precise way of measuring moisture and oxygen levels is to install an oxygen analyzer and dew point meter. It's inexpensive and highly accurate. If a green oxide film is forming on your stainless steel parts, that's an indication that the furnace or atmosphere is not optimized.

For a complete evaluation and audit of your process, give us a call at 800-654-4567.