Dehumidifier Corroded Ground Connections

I took our 3 yr old Kenmore dehumidifier apart to clean it up. It was very clean inside except one area where two ground wires are screwed onto a steel plate which in turn was tacked onto the evaporator which appears to be aluminum fins with copper gas tubes running through them. I'm thinking of removing the two grounds from the corroded plate and using a wire nut or Marr connector to join them together. Then add a third wire, probably #14 copper, from the wire nut to the copper tubes. I'm not sure how to connect this third wire onto the copper tubes though. Any suggestions? Is there a better method of performing this repair? Attachment 45817 (http://www.doityourself.com/forum/attachments/humidifiers-dehumidifiers/45817-dehumidifier-corroded-ground-connections-img_2998.jpg)