Broken off heater valve. An alternative to drilling it out.

[JohnD]

Because of the electrolytic corrosion when two different metals are in contact, the iron heater valve usually becomes fixed inside the aluminium inlet manifold.   Try to unscrew it, and often it will break off, leaving the threaded part embedded in the manifold.    The usual advice is to drill out the stub, as an E-Z-out is likely to break too, making matters worse.     Here's an alternative, that I can't test, but may be worth trying.    It works like chemical engineering judo, using the same effect that caused to problem to cure it!

When iron and alumiium are in contact, and form a battery cell, it's the iron that corrodes, as it has a lower potential.    Promote that and speed it up, and the iron will corrode away!     A battery needs an electrolyte, and a convenient substance is alum, aluminium double sulphate (Al(SO4)2, readily available on eBay. Make up a saturated solution in water, as much alum as will dissolve, and immerse the part in it.    Heat may help speed up the reaction, but I'd suggest no more than a radiator, or warm airing cupboard, as this may take many days.

I no longer have that sort of inlet (or a heater!) so I can't test this for myself.    But it's not going to damage anything, so worth a try, if anyone is in this position.

John

[JohnD]

It occurs to me, that this electrolytic treatment might be accelerated in the same way as electrolytic rust removal.    If the sacrificial anode (??) were connected to the iron stub, it might erode a lot quicker!

[SpitFire6]

Hi,

 My understanding is that Fe + Al = Aluminium is the Anode and corrodes. Cathodic Protection CP.

Passing current the wrong way thru Fe + Al in an electrolyte will cause the Iron to corrode. Impressed Current. (Reversed).