I came across some interesting information regarding this corrosion, though from a different angle. Have a look at the attached documents from A.O. Smith on aluminum hydroxide as it pertains to water heaters. The substance is described as similar to what Daox found in his heater core (or matrix) and is caused by water with high PH:
A.O. Smith lists a product to treat this that they call Un-Lime. In their Bulletin 14 (attached) they recommend using Un-Lime heated to remove the aluminum hydroxide.Originally Posted by A.O. Smith
In another document (also attached) A.O. Smith lists a different procedure for using Un-Lime and in it they stress to not allow the solution to come in contact with the sacrificial aluminum anode rod:
Originally Posted by A.O. SmithIf most of the Mirage cooling system is composed of aluminum - engine block, heater core, radiator, water pump - it sounds like using an acidic solution could/would be harmful.Originally Posted by A.O. Smith
In another section of the document A.O. Smith has the following:
TERMS DESCRIPTION REMOVED BY PROBLEM CAN BE REDUCED OR ELIMINATED BY Water Scale - Lime (Hard Water) Calcium and Magnesium Carbonate Deliming with Un-Lime Professional Delimer. Water softening or feeding glassy phosphates Water Scale - Other Silicates, Sulfates, Aluminates, etc. Manually scraping Cannot be eliminated but effect can be greatly reduced by periodic deliming with UN-LIME. Silt Fine particles of soil or sand suspended in or deposited by water. Flushing Clarifier Filter
This suggests that when it comes to what Daox found fouling his heater core, there may be no solvent that can flush it out. Preventing PH levels from getting out of hand may be the best approach to dealing with this.