can't identify the root cause of the rust

Hi guys,

Give the reasons of rust form on the copper-alloy. Beyond the liquid, atmosphere condition.

Corrosion - you need oxygen and metal, or two materials at different galvanic potential and a path between the materials.

Eliminate any one of the above three to stop the corrosion.

See: [URL]http://www.engineersedge.com/galvanic_capatability.htm[/URL]