Heat Exchanger Ground

[Mike and Joanne Stimmler]

I'm is the process of cleaning and repainting my HX and I know that for the zinc to function properly it must have a good metal to metal contact where it threads into the HX. So I'm thinking that the HX  mounting bracket that mounts to the engine block also should have a good metal to metal contact to provide a good ground for the HX to work properly. Does this make since? Should I clean the paint off so that I  have a bare metal spot on the bracket where it's bolted to the engine?

Also, do I need to use permatex on the rubber gaskets and O rings.

Mike

[Stu Jackson]

Mike, just the opposite.  I even put a doubled thickness bicycle inner tube between the HX and the bracket.  

The zinc works on the metals within the HX body itself.  Whether the HX body is "floating" as mine is, completely electrically isolated from ground (engine) by the hoses and my inner tube, or whether it's connected directly doesn't matter.

It's not electrical corrosion, it's galvanic corrosion.

[Ron Hill]

Mike : As Stu said it's galvanic electrolysis that you're worried about. 
You shouldn't need any Permatex II on the end cap gaskets as they should seal themselves- just don't crank then down too tight - make sure the edges are clean of any corrosion. 

[mainesail]

Mike : As Stu said it's galvanic electrolysis that you're worried about. 
You shouldn't need any Permatex II on the end cap gaskets as they should seal themselves- just don't crank then down too tight - make sure the edges are clean of any corrosion. 

I used a diamond stone, like for sharpening a knife, to hone the HX bronze ends and then filled all the pin holes with thickened epoxy and re-honed them. The HX ends are sloppy to say the least and are famous for leaking. On top of that I polished up the end caps and then used a generous amount of Tef-Gel on either side of the gasket. Since doing this I have not had but one drip or sign of a drip from the HX end caps..

You should not need to do all this but the QC on these HX's is horrible..!

From the factory it leaked:


This was taken during the honing. Notice all the pin-holes and the high spots..


Take these extra steps, use some Tef-Gel and you'll never leak again...

[Mike and Joanne Stimmler]

Thanks for all your replies.

I was thinking that galvanic corrosion = electrolysis and requires electrical grounding like the boats that have metal through hulls and have them connected to a common ground to prevent electrolysis.

Also, should I be concerned about masking off the hose barbs of the HX when I spray it or is paint on them OK?

[mainesail]

Also, should I be concerned about masking off the hose barbs of the HX when I spray it or is paint on them OK?

Mask them or you'll most likely wind up with leaks in the future.



Zinc Chromate Primer

[Mike and Joanne Stimmler]

Thanks again.