De-Zinced or Not?

[Yara]

Here is a pic of a toilet seacock with evidence of some form of corrosion. Do our wise readers think it could be de-zincification? Age is probably 30+ years. The other problem is that there is no marking to indicate the closed position, and the handle was not attached to the spindle. Does the square end orientation tell us something?

 

[VicS]

Id not think the light deposit of copper salts on the outside significant at all.

If the valve is brass dezincification on the inside would be of concern. See Vyv Cox's website for information about, and examples of, dezincification. At the age you say it could well be bronze anyway and not even dzr brass.

Of what I can see in the picture I would be a little concerned about the stainless steel bolts, esp. if that is a "rust" stain visible between the 12 and 3o'clock positions. It could indicate that crevice corrosion is occurring.

Blakes normally supply phosphor bronze bolts ITYWF.

If you must fit stainless bolts ensure that they are well sealed into the holes so that there is no scope for crevice corrosion to occur. They must of course be 316 grade.

See Vyv's website for info on crevice corrosion.

http://coxengineering.sharepoint.com/Pages/default.aspx

 

[onesea]

Must admit I would check that one probably hit it with hammer when boat was ashore? Although others with knowledge would give better reports...

In the mean time to check the valve status if ashore undo 2 nuts service and check the valve out grease it.... If Afloat pump the loo gently and turn the valve till it runs. There is some logic in the orientation the nut will be as a diamond. Tradition has it if the handle is in line with the pipe the valve is open across closed....

 

[sarabande]

IIRC the 'diamond' has a line across from one corner to another to indicate direction of flow.

 

[Yara]

Thanks gents, What you say makes sense. Stainless bolts are a worry. If I buy the boat I will change them. The inlet valve is even worse, with one of the bolts sheared off!

 

[Tranona]

Think you will find that is not a Blakes valve but a Rowe or Simpson Lawrence of similar design. Housing and cone are bronze so should not have any corrosion problems. As suggested the fastenings should also be bronze, but they are not the same bolts as Blakes. In the UK you can get bronze bolts to suit from Seaware or Anglia Stainless.

 

[MM5AHO]

Echo comments on de-zincification. Normally on the wet side its seen, not the air side.
On valve positions, the line cut into the top of the square stem of the valve indicates the position. In line with flow is open, across the flowline is shut.
Our toilet seacock is the same as this. Handle is easy to remove and put back on at 90 degrees.