Inspection of Brass Tapware

I have known of a parallel example of galvanized steel evaporator coil in an ammonia refrigeration system. There was a pinhole leak in the steel which was not detected prior to the hot-dip galvanizing. The coil then passed the underwater air test and also survived for a while after installation. Eventually the ammonia, passing through the pinhole, corroded the zinc and caused a leak.

I suspect your brass casting likewise had a defect that the chrome plating "papered over" for a while. How the chrome would then corrode away I don't know, so this is just a guess.

The pressure is rather low, so "Bondo" or epoxy might make a successful repair. Or else you might be able to buy a new spout as a spare part.

I think your theory is probably valid. I was at one time involved in discussions on whether pipelines should be painted before or after pressure testing. I no longer remember the exact details, but we drilled a small hole in a test section of 6" schedule 40 pipe. We then painted the pipe with a single coat of PA10 (I think) and applied pressure. The result - a well painted over hole of 3mm diameter withstood a hydrostatic pressure test of 20 bar.

I guess a decorative chrome layer would do just as well over a very small casting defect.

Thanks you for the post.

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Mr/Ms Editor, are you referring to my thread as being 'Off topic'?

After all I am the originator. However if I have got the message wrong, I apologise.

To Tornado, Prof and Pokemont, thank you. Can we now put our minds to the question of a visual test that would show up the imperfections in the casting?

Brian.

Brian

Two points,

I would assume that the 1500kpa pressure test would only be on the high pressure side. I suspect that no pressure testing is done on the spout as this merely directs the flow into the sink. (I'm not up on testing processes, but I could see that it really isn't necessary to pressure test a non pressuirsed part of the component). You are prob correct that the chrome plating was previously stemming the leak.

As the hole is presumably on the underside of the spout ("sprays water down, fortunately, into the sink"), I would use some form of epoxy to plug the hole such as Araldite, Epoxy Filler, (car or builders bog) etc. It probably won't be seen. As the brass is fairly inert the hole should not continue to erode, so a filler would presumably provide a permanent fix.

Cheers

Tony

Thanks you for the post.
Hi guys, Im a newbie. Nice to join this forum.

Good thinking! You are probably correct come to think of it.

Repairs are not necessary as there is a 'Life time warranty' on these things. I am getting a new complete mixer tomorrow. Also DIY installation does not void the warranty. Good eh? My original post was a bit academic to see if any type of inspection would find holes in the casting.

Thanks all. Brian.

I believe you can xray components to show up flaws in castings. Prob not worth the cost for tapware production, though.

Part of what you are suggesting is incorrect i am afraid. I work for as an QC engineer for a tapware company. The leak tightness test are carried out after the chrome plating process. That part's true. But as all cast and forged brass parts in tapware manufacturing the spouts are tested against leakage via air pressure. the common standart for the spouts is 6 bars of air pressure with 20 mbars of leak allowed at a period of 3 secs. testing. The australian standart requires brass that is resistant to dezincification. That would very much prevent the chemical damage on the brass but as for the mechanical damage it is unavoidable. The only way to avoid is to use ceramic cartridges or headworks.