Without repeating all the stuff on the post about "Marine Brass?" the subject of TONVAL has not been addressed and perhaps should be. Many suppliers are selling skin fittings and valves in this material and the implication is that it is suitable for underwater use. My question is simply this.... Does ANYONE know what it is? I mean specifically? What is its chemical composition? Where does the term come from? Has anyone seen any test data on it or have any reason to believe it is suitable and will resist dezincification? Or are we all just accepting the publicity without question?
Nothing to add that isn't already in the 'Marine Brass' thread, but as boatmike suggests, this is IMPORTANT. Somebody out there must know. But if they don't...well, QED, the stuff's a pig in a poke
Don't know the composition - Tonval ATD is a corrision resistant but may suffer from dezincafication. It is perfectly suited for above the water line and many yachts have it below the waterline without any problems.
"Tonval ATD: The trade name given to the 60/40 leaded brass used in themanufacture of through-hull fittings. The closest ISO material designation is CW619N and the material symbol designation is CuZn40Pb2Sn.
CW619N: A brass suitable for wrought and unwrought forging with the composition: copper 57-59%; aluminium 0-0.1%; Iron 0-0.4%; Nickel 0-0.3%; lead 1.6-2.5%; tin 0.2-0.5%; remainder zinc (approx. 38-40%).
The trade name Tonval, in the UK, conceals rather than conveys the nature of the material used for the through-hull fittings. To ensure that buyers of these products are fully aware of the nature of the material, such fittings should be clearly described as made of a “brass (not inhibited against dezincification)”."
If that's the case Roberto my suspicions are verified. Thanks for the information. Retailers (and there are many) who describe this material as Tonval Bronze are telling lies. It definitely ain't bronze and if, as you say, it is a brass that is not even inhibited against "de-zincing" should, as I originally thought, never be fitted below the waterline.
As luck would have it my new ASAP catalogue just came through the door. In it there are through hull fittings in Gunmetal (excellent) Perko (trade name) fittings in what are called "cast bronze" (lord knows what sort though) 316 stainless steel ones. (should NEVER be fitted below the waterline in my opinion) and guess what? What they call TONVAL BRONZE ones! There are also other fittings such as hose tails that are Lloyds approved in DZR and TONVAL BRONZE ones too. So it's obvious to me that we should NEVER fit tonval anywhere on the boat that comes into contact with seawater. It's also evident that GUNMETAL fittings are still widely available and should be used for this purpose.
I just had a saved copy of the report, I found the <A target="_blank" HREF=http://www.dft.gov.uk/stellent/groups/dft_maritimesafety/documents/page/dft_masafety_027359.pdf>original one here </A> anyway
Your statement should read "without any problems YET!
These components are safety critical, its like bunjee jumping on knicker elastic.
As it breaks you hear the protest..... I NEVER HAD THIS PROBLEM BEFORE !!!!!>>>>>
My ASAP catalogue(7th Edition) has the note:-
"Tonval ATD - Has corrosion resistance but is susceptable to dezinctification. Bronze UNI 7.13/8 G-CuSn5ZnSPs - Frequently known as Gunmetal" But no spefic recommendation as to where they should be correctly used.
BUT this note is on the Seaflow Pipe Fitting page, which is 2 pages AFTER the 'Through Hull Fittings/Seaflow Hose Tail Fittings' pages. There should be a definate note concerning Tonval ATD such as "Tonval ATD must NEVER be used underwater"
<hr width=100% size=1>dickh
I'd rather be sailing... :-) [img]/forums/images/icons/smile.gif[/img]
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dickh
I'd rather be sailing... :-) [img]/forums/images/graemlins/smile.gif[/img]
10 years and counting... Hammer test every year. The point was made on the other thread it depends on the stray currents around - no problem on a swinging mooring, bit of an issue in a marina.
Anyway don't you have hard wood bungs next to the skin fittings - I do even where I have LG2 fittings for the heads!
There is a risk with Tonval but if inspected it is manageable.
PS My Asap catalogue quite clearly states at the top of pages on pipe fittings that it is only corrosion resisting. The problem often is that for pipe fittings you can really struggle to find some combinations in anything else
What the hell is TONVAL???
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