Experimental investigation help about corrosion.

[popsterrockz]

Hi, I need some help regarding my assignment which is due next week. We are investigating about metal corrosion on copper. we did a variety of ph solutions, ph 3, 5, 7, 9 and we have to find out which solution promotes more corrosion. we know it would be the acidic one but we have to explain it. We made ph 3 by accurately mixing HCl and NaOH until we have ph 3 and after a week or so. we found the copper corroded and went purple.. here is the image..

i dont know what happened to it. im expecting light green because of the patinas.. can anyone help me.. and for the equations, will it be copper chloride forming? please help