Skin fittings mixing brass and bronze

petem

petem

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I'm just looking at the collection of skin fittings, valves etc that the A/C company left on board for the A/C fitting to be completed. This is the list:

Inlet

GRATED BRASS SKIN FITTING (http://aquafax.co.uk/product/2-70212-grated-brass-skin-fitting-34bsp)
DZR BRASS BALL VALVE (http://aquafax.co.uk/product/1-70902-dzr-brass-ball-valve-34bsp-2281)
BRONZE FISHERMAN WATER STRAINER (http://aquafax.co.uk/product/2-70152-fisherman-water-strainer-bronze-34bsp)
CONNECTOR BRONZE (http://aquafax.co.uk/product/1-72112-connector-bronze-34bsp-34-hose)

Outlet

BRONZE SKIN FITTING (http://aquafax.co.uk/product/2-70102-skin-fitting-bronze-34bsp)
DZR BRASS BALL VALVE (http://aquafax.co.uk/product/1-70902-dzr-brass-ball-valve-34bsp-2281)
BRONZE CONNECTOR (http://aquafax.co.uk/product/1-78815-bronze-connector-34bsp-16mm-hose)

As you can see, there's a mixture of brass, DZR and bronze. Is it OK to mix these in a single fitting?
 
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ASAP supplies offer the inlet scoops in DZR brass and bronze. Seems a shame to fit an ordinary brass one when all the other bits and pieces are either bronze or DZR.

Mixing bronze, DZR brass and ordinary brass though is no problem
 
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My last boat, many years ago, a Coronet, a good solid boat, had bronze fittings everywhere so I assumed this was the norm. Sadly not. I've ripped all the OEM brass stuff out of my Princess and replaced it with DZR and bonded it. Don't know how long I will keep her, so failed the man-maths challenge to replace it all with bronze.
 
Sorry to put two posts up here when one would have sufficed, but agree with burgundyben's reply to post 3. Suggest Googling galvanic potentials as a starter.
 
As absolute minimum the first item absolutely shouldn't be accepted. As for the rest I would do all bronze but your (pointless) pic n mix will be ok for long enough if bonded.
 
jfm said:
As absolute minimum the first item absolutely shouldn't be accepted. As for the rest I would do all bronze but your (pointless) pic n mix will be ok for long enough if bonded.
Click to expand...

Thanks JFM and others. They're not bonded so (for the avoidance of doubt) if I swap item 1 for a Bronze fitting will that be OK or should I try and replace the DZR BRASS ball valves with bronze too (which would mean going to another brand / supplier as Aquafax don't do my size in Bronze)?
 
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burgundyben said:
Why is the brass ok?
Click to expand...

There is no problem mixing brass with DZR or bronze, although brass would not be a good choice when there are DZR or bronze fittings available. All these materials are virtually the same on the galvanic scale so there is no need for anodes. Bronze skin fittings and DZR valves are very common together as until recently DZR skin fittings were not generally available.

So, as already suggested replace the brass skin fittings with bronze or DZR.
 
I concur with the last sentence of JFM's post #7 - bond it all together and to your anodes. The time and cost of doing this is absolutely negligible in the scheme of things and IMHO will also add some protection if you start to get stray currents from failing float switch connections in the bilges, or a current leak in the genny.
 
@Tranona: yes, brass, DZR and bronze are relatively close in the electrochemical series, but IMO nowhere near close enough, otherwise we would all be using brass and there would be no market for fittings made from bronze or DZR! 80- 100mV delta has a huge effect when one of the metals is very gently fizzing away 24/7/365. Please explain why there is no problem mixing them and why we should avoid the very trivial task of bonding, have you ever had stray currents dumped into your bilges?
 
I think I'd rather avoid putting bonding in (it's beyond my own capability) and I wouldn't trust a foreign contractor to do it correctly. I suspect that poorly installed bonding might actually be more of a risk than a benefit.

If I was spec'ing a new large boat I'd certainly include them but Fairline didn't feel the need to install them in my boat in the first place so I'm not convinced of the benefit. Incidentally AFAIK Princess don't bond their seacocks either.

It would however appear than an all bronze set up would be wise so I'll swop the brass and DZR fittings for bronze ones.
 
P, out of curiosity, was my guess about the 90deg bend being brass, in this pic which you posted in the "Andiamo" thread?
If yes, it's easy to see why going all bronze wouldn't be a bad idea... :encouragement:
20171230_150005.jpg
 
MapisM said:
P, out of curiosity, was my guess about the 90deg bend being brass, in this pic which you posted in the "Andiamo" thread?
If yes, it's easy to see why going all bronze wouldn't be a bad idea... :encouragement:
Click to expand...

P, I don't know the answer. The verdigris colour of the valve and bend is the same. I don't know if there's any marking on them to indicate what they are made of either.

Incidentally, the seacock with the (external) corrosion is adjacent to another that looks much healthier (no verdigris)...

20170602_112807.jpg


I wondered if one of the two may have been corroded due to condensation dripping onto it over the years. Since owning the boat, I have cleaned that area of the bilge (including the rust stains) and it's remained totally dry.
 
Petem, bonding skin fittings is quite simple but DON'T do it like cross-bonding various bits of metal in your bathroom to each other. I bonded each skin fitting seperately and directly back to the busbar on the back of my anodes, with absolutely no other connections between skin fittings. I expect some bright spark will write in now and try to explain I did it all wrong, lol.
 
re the verdigris on the elbow - give it a really good clean with a Brillo pad and see if it comes up gold. if its pinkish time to get rid.
re bonding I wouldn't bond them. Once they are connected into the anode circuit they are part of the galvanic system of the boat.
If they are not connected (like your other skin fittings etc) they are electrically isolated, (internal connections are via plastic/rubber hoses) independent of the other underwater metal bits and do not take any part in the galvanic process that effects your outdrives etc. As you now plan to use bronze on all the new bits they will effectively be inert.
The only boat we had with bonded skin fittings was a 1980 princess 37. The other five (fairlines/princess/sealine/rodman) do not have bonded skin fittings only the shaft/P bracket and rudders where mixed metals are in direct electrical contact under water.
 
I think I now know why they spec'd a brass scoop. This is what they supplied...

http://aquafax.co.uk/product/2-70211-grated-brass-skin-fitting-12bsp

As you can see, the slots are full length to prevent 'scoop effect'. Aquafax don't do a bronze version to my alternatives would be a round one like this...

http://aquafax.co.uk/product/2-70242-bronze-grated-skin-fitting-34bsp

Or a DZR one like this from ASAP...

https://www.asap-supplies.com/fitti...ed-raw-water-intake-through-hull-scoop-402524

Would the round one give sufficient water flow? What intakes do others have for their A/C?
 
Sorry Petem, shafts on mine, I forgot you have outdrives on your new boat, aka devil's eggwhisks I believe they are called on here.
 
petem said:
What intakes do others have for their A/C?
Click to expand...

The Maestrini one .DZR scoop type .
So that you can run the AC and geny underway .
Not done often in a boat that size , btw .
One day after a season or two you may fit a geny so don’t rule out running the AC underway .
Keep all options open
 
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