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Metals question (20 posts / 1,062 views)
duggs
Posts: 5,559
Post #1 2 Dec 2020 08:43
0
I've ordered some bits to knock up a little camera support widget, the main body I'll make from Ali billet, but I was going to use brass for the threads, do I need to use something to prevent bimetallic corrosion?
carpstar40 carpstar40
Posts: 3,706
Post #2 2 Dec 2020 08:51
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In reply to Post #1
I always thought that bimetallic reaction was between any form of mild/galvanised steel and any other dissimilar metal, I work with and use a lot of stainless steel in construction fitted to mild steel frames and they always have to be isolated from each other, it also has a lot to do with the amount of surface area covered the greater the area with stainless the quicker and more accelerated the corrosion, I would of thought aluminum and brass would be fine.
duggs
Posts: 5,559
Post #3 2 Dec 2020 09:29
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In reply to Post #2
I'm not sure mate, but lots of metals react with each other. I've had grief in the past with galvanised steel and copper, steel and copper....
Google says aluminium and brass are a no no but most fishing metalware is Ali with brass threads
In fact it says Ali, brass and stainless shouldn't be mixed with each other especially in threaded joints
carpstar40 carpstar40
Posts: 3,706
Post #4 2 Dec 2020 09:35
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In reply to Post #3
Yes strange one, I've never had an issue with brass inserts with ali or stainless just about mixed matched all forms of these with banksticks, landing nets, buzz bars and angle adapters from Gardner, Jag and Solar never seen anything untoward.
duggs
Posts: 5,559
Post #5 2 Dec 2020 09:57
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In reply to Post #4
Yeh me neither, I'll see if the resident metallurgist pipes up before I order the rod though

It'll have some expensive kit mounted on it so I thought I'd check
yonny yonny
Posts: 7,934
Post #6 2 Dec 2020 10:04
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In reply to Post #5
Google the galvanic chart Dave, it'll tell what's compatible with what.

Edit: neither brass or ali rust like steel as there's no iron in them. You might get some white/green residue but tbh I'd not worry about it too much mate.
duggs
Posts: 5,559
Post #7 2 Dec 2020 10:55
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In reply to Post #6
Thanks mate, I'd have to have a science lesson to understand that chart, I cut wood for a living

It looked to me like Ali shouldn't be mixed with brass or stainless, but if it's not gonna rot I'll carry on
sundance sundance
Posts: 6,762
Post #8 2 Dec 2020 11:15
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proud boast.
the brass on my Defiant pod had developed a blue-white crust after 3 years on the floor of a damp garage.
1 week in a cup of ketchup and they were like new.
Hitman Hitman
Posts: 9,171
Post #9 2 Dec 2020 14:26
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At work we use red fibre washers between brass and galv material 👍
duggs
Posts: 5,559
Post #10 2 Dec 2020 14:56
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In reply to Post #9
I'll probably set the threads in place with epoxy, that should help keep them separated and also stop them coming loose.
carpstar40 carpstar40
Posts: 3,706
Post #11 2 Dec 2020 15:25
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In reply to Post #6
Baffled me as looking at the Stainless/Nickel likelihood of corrosion it is a definite that there would be reaction yet both 304 and 316 stainless has albeit a lowish Nickel content of 8 to 14% and from what I believe is what drives the price behind the cost of buying stainless, am I missing something is it that contact between the two separate isolated materials causes the reaction if not isolated from each other rather than it being included in the raw state material.
duggs
Posts: 5,559
Post #12 2 Dec 2020 16:04
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In reply to Post #11
I was lost at cathodes and anodes
framey framey
Posts: 5,319
Post #13 2 Dec 2020 19:11
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I would have thought the only time you will need to even vaguely worry about it is if it gets wet
I'm sure you won't be letting camera get wet.
Depending on camera you may even have a stainless thread in the bottom of that so you will now have 3 metals to worry about lol
duggs
Posts: 5,559
Post #14 2 Dec 2020 19:58
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In reply to Post #13
My camera is well sealed, I have no qualms about using it in a shower, the mount though will be used when fishing and will stay on the bankstick overnight. A head then mounts above this with a quick release mechanism so I just have to clip the camera in and its good to go, no messing about lining everything up.

So yes it will get wet

I'm not sure if any catalyst was involved but I've found holes in copper pipes where they've been contacting galvanised steel, and that's in weeks in a dry environment (at least it was before the holes appeared )
Old-Cornishman
Posts: 688
Post #15 3 Dec 2020 14:17
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In reply to Post #7
The aluminium will sacrificially corrode before the brass so if the main body is aluminium then presumably you will more metal to sacrifice so I wouldn't worry too much.
If you really wanted to be fussy you could use anti corrosion compounds or better still fit a fibre washer between the parts as per hitman.
Always better with a washer to mechanically protect the parts anyway.

I also cut wood but only as a hobby / for my own use. Enjoyable job you've got there I would think.
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