Mixed metals in a cast aluminium radiator.

[p45cal]

I have some die-cast aluminium water-filled radiators which I need to fit reducing bushes to.
One supplier suggests brass ones would be needed as there are no problems corrosion due to mixing metals...
but another suggested steel ones would be needed!

I need a third (or more) opinion please!

 

[bewsh]

To be honest they'll both cause corrosion due to electrolysis.

 

[p45cal]

To be honest they'll both cause corrosion due to electrolysis.

Thank-you. When I got to the radiators, it turned out the original end caps were iron, had been there 30 years and there was minimal (if any) corrosion of either the iron or the aluminium, so I went for iron reducing bushes.

 

[FD Powerflow]

Provided you give them a good wrap of PTFE tape and then add a decent molybdenum based inhibitor to the system water you shouldnt have an issue.

 

[DirksPlumbing]

Provided you give them a good wrap of PTFE tape and then add a decent molybdenum based inhibitor to the system water you shouldnt have an issue.

Provided you can ensure zero gaps and a flawless cover of PTFE tape. Other than that steel should have lesser impact. Third option would have been stainless steel.
But yes you are right, if you can minimise oxygen intrusion into the system then there should not be any issues with corrosion. If you then can ensure a pH value of 7 and above you are on the safe side.

I have found myself using steel fittings to sacrifice them over corroding away the appliances connections.

 

[p45cal]

Provided you give them a good wrap of PTFE tape and then add a decent molybdenum based inhibitor to the system water you shouldnt have an issue.

Thank-you both.
Well! Confusing or what?
AEL's/Faral's assembly guide says "Do not use any jointing paste or tape (PTFE or similar) to the gasket, nipple threads or radiator", and their general installation guide for aluminium radiators says "No thread sealant paste or tape may be used on the thread or bush which mates into the radiator."
There was no evidence among any of the 5 end caps I removed of any PTFE or jointing paste/compund whatsoever (they were iron and they were original ones maked 'Faral'). So I didn't use any. (They do however advise use of PTFE on the pipe fittings that are screwed into the reducing bushes.)

So now some advice on the best inhibitor to use bearing in mind that these radiators contain water which is static now as they've been converted to electric (and so far sem to work very well)?

I tried to include a couple of links to the two guides mentioned above (there's even a special little link icon to do just that in the advanced message composition), but I wasn't allowed to post them - and to add insult, it cleared the whole message so I had to rewrite it all again.

I think I've managed to attach these files instead.

 

[FD Powerflow]

Im not a fan of the "no thread tape or sealant" part of their instructions! I can only assume as per Dirks comment, they use steel connections to be the sacrificial part of the system. As for inhibitors most people on here will direct you to Fernox F1 or Sentinel X100, tried and tested and you can even test their level annually.

 

[p45cal]

most people on here will direct you to Fernox F1 or Sentinel X100, tried and tested and you can even test their level annually.

Thank you! I'll check them out.