stainless ball valve on ?bronze skin fitting

bikedaft

bikedaft

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old plumber's merchant ball valve handle has rusted away, tho valve/body seems fine

got a new 316 stainless ball valve (with s/s handle!)

any problems mixing it with a probably 40yr old ?bronze skin fitting?

will use ptfe anyway to make sure orientation is correct when screwing it on

thanks
 
Replace the hull fitting too. SS & Bronze are too far apart on the electro-compatibility scale. There will be electrolytic corrosion. With a 40 year old fitting it's possible that there will be some fretting on the threads, too which will make things worse. PTFE tape isn't the answer unless you are looking for a short term bodge to get you home.
 
last time i had this valve off the skin fitting was perfect. and the boats in the water

so will put another non stainless one on then, inspecting the threads etc as i go

thanks
 
If I recall correctly from Nigel Calder's book, 316 stainless is so very near bronze on the galvanic scale that it can be used with a bronze thru hull. I can get the book off the boat at the weekend and scan the relvant page for you if you wish.

That being said, not mixing materials is the preferred solution but your seacock is not going to fall off after a short time if 316 or 316L stainless is used with proper bronze.

It's not the case for most other grades on stainless though.
 
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ok, thanks

am only assuming skin fitting is bronze as its lasted well. however it could have been changed by a previous owner etc

if you hear of a boat sinking at mooring in the gareloch tonight it was me ;-)

(don't worry i got plenty soft wood plugs)
 
You may find that a local plumbers' merchant will stock DZR ones. In soft water areas they are quite common, as dezincification occurs there. You want one with the CR mark cast in. Otherwise ASAP sell them, not very expensive.
 
Corros1.gif
 
thanks

the thru hull thread looks fine, no pitting/dezincification etc. stuck another cheap valve on but will get a dzr and change it over

should have done that first, but just though "old one corroded, get 316" doh
 
Please see items 53 and 54 below
316 and bronze Looks Ok to me. I believe 56 "red brass" = gunmetal

The following galvanic table lists metals in the order of their relative activity in seawater environment. The list begins with the more active (anodic) metal and proceeds down the to the least active (cathodic) metal of the galvanic series. A "galvanic series" applies to a particular electrolyte solution, hence for each specific solution which is expected to be encountered for actual use, a different order or series will ensue. In a galvanic couple, the metal higher in the series (or the smaller) represents the anode, and will corrode preferentially in the environment. Listed below is the latest galvanic table from MIL-STD-889 where the materials have been numbered for discussion of characteristics. However, for any combination of dissimilar metals, the metal with the lower number will act as an anode and will corrode preferentially. The table is the galvanic series of metals in sea water from Army Missile Command Report RS-TR-67-11, "Practical Galvanic Series." (reference)

Active (Anodic)

1.Magnesium
2.Mg alloy AZ-31B
3.Mg alloy HK-31A
4.Zinc (hot-dip, die cast, or plated)
5.Beryllium (hot pressed)
6.Al 7072 clad on 7075
7.Al 2014-T3
8.Al 1160-H14
9.Al 7079-T6
10.Cadmium (plated)
11.Uranium
12.Al 218 (die cast)
13.Al 5052-0
14.Al 5052-H12
15.Al 5456-0, H353
16.Al 5052-H32
17.Al 1100-0
18.Al 3003-H25
19.Al 6061-T6
20.Al A360 (die cast)
21.Al 7075-T6
22.Al 6061-0
23.Indium
24.Al 2014-0
25.Al 2024-T4
26.Al 5052-H16
27.Tin (plated)
28.Stainless steel 430 (active)
29.Lead
30.Steel 1010
31.Iron (cast)
32.Stainless steel 410 (active)
33.Copper (plated, cast, or wrought)
34.Nickel (plated)
35.Chromium (Plated)
36.Tantalum
37.AM350 (active)
38.Stainless steel 310 (active)
39.Stainless steel 301 (active)
40.Stainless steel 304 (active)
41.Stainless steel 430 (active)
42.Stainless steel 410 (active)
43.Stainless steel 17-7PH (active)
44.Tungsten
45.Niobium (columbium) 1% Zr
46.Brass, Yellow, 268
47.Uranium 8% Mo
48.Brass, Naval, 464
49.Yellow Brass
50.Muntz Metal 280
51.Brass (plated)
52.Nickel-silver (18% Ni)
53.Stainless steel 316L (active)
54.Bronze 220
55.Copper 110
56.Red Brass
57.Stainless steel 347 (active)
58.Molybdenum, Commercial pure
59.Copper-nickel 715
60.Admiralty brass
61.Stainless steel 202 (active)
62.Bronze, Phosphor 534 (B-1)
63.Monel 400
64.Stainless steel 201 (active)
65.Carpenter 20 (active)
66.Stainless steel 321 (active)
67.Stainless steel 316 (active)
68.Stainless steel 309 (active)
69.Stainless steel 17-7PH (passive)
70.Silicone Bronze 655
71.Stainless steel 304 (passive)
72.Stainless steel 301 (passive)
73.Stainless steel 321 (passive)
74.Stainless steel 201 (passive)
75.Stainless steel 286 (passive)
76.Stainless steel 316L (passive)
77.AM355 (active)
78.Stainless steel 202 (passive)
79.Carpenter 20 (passive)
80.AM355 (passive)
81.A286 (passive)
82.Titanium 5A1, 2.5 Sn
1.Titanium 13V, 11Cr, 3Al (annealed)
2.Titanium 6Al, 4V (solution treated and aged)
3.Titanium 6Al, 4V (anneal)
4.Titanium 8Mn
5.Titanium 13V, 11Cr 3Al (solution heat treated and aged)
6.Titanium 75A
7.AM350 (passive)
8.Silver
9.Gold
10.Graphite
 
thanks

but is no 53 stainless 316L not the low carbon s/s for welding, as opposed to the no 67 stainless 316 which (presumably?) the valve body/ball are made off as no requirement for welding?

bit out my depth here...

ordered a marelon valve also to trial
 
bikedaft said:
thanks

but is no 53 stainless 316L not the low carbon s/s for welding, as opposed to the no 67 stainless 316 which (presumably?) the valve body/ball are made off as no requirement for welding?

bit out my depth here...

ordered a marelon valve also to trial
Click to expand...

The 'active' figure should not be used to compare with other alloys. The difference between the 'active' and 'passive' voltage represents the driving force for a single alloy in crevice corrosion. In the list above the voltages are not shown but there are versions where they are. Sorry, don't have a link to that detailed data.
 
vyv_cox said:
The 'active' figure should not be used to compare with other alloys. The difference between the 'active' and 'passive' voltage represents the driving force for a single alloy in crevice corrosion. In the list above the voltages are not shown but there are versions where they are. Sorry, don't have a link to that detailed data.
Click to expand...

thanks

will stick to dzr/bronze/plastic
 
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