Attached is the SEM EDX (explanation) analysis of the cooling channel. As you can see the material is deeply pitted by galvanic corrosion. X-ray spectroscopy also detected the presence of silver. Perhaps silver filled high thermal conductivity epoxy was used in the construction? In any case it appears to be a pretty straight forward case of galvanic corrosion between the dissimilar components in electronic contact with each other and a wet environment.

[Silver eopxy is indeed used, between the tube bend and the Aluminum end block, grounding the tube and the carbon foam].

Wed Feb 06 22:32:41 2013
Filter Fit    Chi-squared value:  24.711   Errors:+/-1 Sigma
Correction Method:  Proza (Phi-Rho-Z)
Acc.Voltage: 10.0 kV  Take Off Angle: 37.1 deg

Element  Element             Wt.%       Atom %  Atom %	
 Line	   Wt.%	 Error		 Error	
C  K	   1.67	+/-0.03	   3.74	+/- 0.06	
O  K	   0.73	+/-0.03	   1.23	+/- 0.05	
Al K	  94.31	+/-0.34	  94.21	+/- 0.34	
Ag L	   3.30	+/-0.11	   0.82	+/- 0.03	
          -------------	  --------------		
Total	 100.00		 100.00