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I have obtained a 2.5 ltr polished aluminium tank to use as an header/expansion tank  near to my back-boiler (at the front of the boat) and another (1 ltr) with a sight window for easy checking and expansion at the other end of the boat (connected to the highest point in the pipework). They will be connected into the system with 2 or 3 ft of  PEX tubing. As there are lots of copper pipes throughout, are the alloy tanks (or any other bits) likely to corrode? If I understand correctly they will not be making a circuit  and as the voltages would minimal if this is wrong, I am hoping the antifreeze/water mix will not be a good enough electrolyte to pass through the plastic pipework to the copper. 

Any advice gratefully received please.


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Aldi specified a SS calorifer and Hep2O pipe rather than copper for use with its 30xx boilers due to the aluminium internals.  Not sure how significant it is.  They did say it's not a problem having brass fittings with Plastic pipe.


Does the antifreeze/anti corrosion additive make the water more conductive?

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Galvanic corrosion of dissimilar metals immersed in an electrolyte can only occur if those dissimilar metals are electrically connected and if the electrolyte is condusive to corrosion. 


So, connect your header tanks to the copper pipes of the heating system with plastic pipe or flexible rubber car heater hose and fill the system with antifreeze or inhibitor with anti-corrosive additive and you'll be fine.


This stuff is pretty good. 



Edited by blackrose
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Thanks folks. I will fit them. Happily reassured!  I remember now that there is copper tubing in the engine cooling system connected with rubber hose. The head and exhaust water jacket are aluminium and the boat is 21 years old and counting with no problem so far....

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