My new division has copper lined incubators in the shared cell culture facility. The interior is rusty and corroded, quite alarming looking The lab manager assured me that this is exactly as it should be. Copper-lined incubators are superior to stainless steel and you let the interior oxidize naturally to prevent contamination. Is this true and I need not worry about the appearance of dirty and poorly kept incubators?

This is a paragraph from the Sigma Aldrich Tissue culture guide

2.4 Incubators

Cell cultures require a strictly controlled environment in which to grow. Specialist incubators are used routinely to provide the correct growth conditions, such as temperature, degree of humidity and CO2 levels in a controlled and stable manner. Generally they can be set to run at temperatures in the range 28ºC (for insect cell lines) to 37ºC (for mammalian cell lines) and set to provide CO2 at the required level (e.g. 5-10%). Some incubators also have the facility to control the O2 levels. Copper-coated incubators are also now available. These are reported to reduce the risk of microbial contamination within the incubator due to the microbial inhibitory activity of copper. The inclusion of water bath treatment fluid (Prod. No. S5525) in the incubator water trays will also reduce the risk of bacterial and fungal growth in the water trays. However, there is no substitute for regular cleaning. (Note “Sigma Clean” Prod. No. S5525 is harmful by inhalation, contact with skin or if swallowed and is also a severe irritant.)

The full guide can be found at the ECACC Handbook - Cell Culture

Historically the major antimicrobial in a tissue culture incubator waterbath is Copper sulphate.