Galvanic corrosion ?

My Commando has Dunstall brass exhaust nuts that have done a perfect job for some 55 years. I also use copper grease on the threads. No corrosion issues.
 
commandofastback said:
After reading the exhaust nut thread and watching Jims heat expansion tests, i ordered a set of aluminium exhaust nuts from Andy Molnar now.
Aluminium in Aluminium is prone to seize and Andy states that the nuts should be inserted with copper anti seize.
I am somewhat unhappy with the though of using copper on aluminium because as far as i know the copper would act as a cathode and the aluminium as an anode.
Meaning the copper would eat the aluminium and maybe ruin the threads.

On the other hand, the galvanic corrosion also needs an electrolyte to work between the two metals.

... and lots of people use a blob of copper paste on the spark plug threads.

The galvanic potential difference between Nickel and Aluminium is even higher.
Zinc would be the other way round (Aluminium would be the cathode and Zinc the Anode)
In the end i will go for ceramic antiseize now.

Whats your opinion ?
Or am i just a natural worrier ? ;)
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Galvanic corrosion ?
 
SteveA said:
Aluminium nuts? I wouldn't do that. Just because I wouldn't do that. They are cheap, and they are light. But, does the weight saving add up to much?

What I have done is used stainless nuts from Pat Seager. And I just bought a second set. Really, they aren't heavy. See below link. Scroll down for a lot of Commando stuff. What they aren't is cheap.

And I still tend to put on a bit of copper anti seize, mainly because the nuts are sometimes hard to start. Rigid mounted engine and fairly rigid mounted exhaust impacts that, Commando should be easier,


View attachment 112337
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Its not about the weight, Its about the same heat expansion as the head.
 
commandofastback said:
Collectors of old german model trains from the 1920s know a phenomenon called "zinc pest". Turned out that, because of the metal shortages after WW1, they used a zinc alloy that was contaminated with other metals. Those parts simply deteriorate to dust. It also happens to some old BING carburettors made of pot metal.
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Or something like Mazak, used in many post WW2 British cars for cast items like door handles. The Chrome was supposed to protect the Mazak! :eek:
 
I'd like to order a set of those beads,... but until they get here...

I have a galvanic reaction question as well. I have CBR600 fork dampers installed in my commando. I turn down and thread the fork cap nuts to fit the commando forks, so it's bare aluminum and steel. I've looked at the galvanic metals chart and that combination isn't highly galvanic at all, so without the presence of an electrolitic liquid, it would almost certainly not be an issue.

Wtbs, I was thinking about doing an "at home" hard anodize to strengthen the aluminum threads a bit, being that 20 TPI is such a fine thread. Anyone here do an at home hard anodize to anything threaded??


** Steve, Is mazak the same as Zamak? The gears on my lathe are made of zamak. So far they are ok, but they have a reputation for being crap....
 
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o0norton0o said:
I'd like to order a set of those beads,... but until they get here...

I have a galvanic reaction question as well. I have CBR600 fork dampers installed in my commando. I turn down and thread the fork cap nuts to fit the commando forks, so it's bare aluminum and steel. I've looked at the galvanic metals chart and that combination isn't highly galvanic at all, so without the presence of an electrolitic liquid, it would almost certainly not be an issue.

Wtbs, I was thinking about doing an "at home" hard anodize to strengthen the aluminum threads a bit, being that 20 TPI is such a fine thread. Anyone here do an at home hard anodize to anything threaded??


** Steve, Is mazak the same as Zamak? The gears on my lathe are made of zamak. So far they are ok, but they have a reputation for being crap....
Click to expand...

CNC Controls

Mazak set a precedent in CNC development with the introduction of our MAZATROL programming language in 1981. And, over the last three decades, we’ve continued to improve upon this programming language.
www.mazakusa.com
 
concours said:
This Beinhart guy....
Seams like fun guy, always after the bier...

Click to expand...

The creator of Werner is a guy called Rötger Feldmann and some of the storys are based on the things that happened during the plumber-apprenticeship of his brother Andy.

Andy has been fiddling around with almost everything that has an engine and he now runs the most entertaining Youtube channel I know (in german I am afraid)

50cc Zündapps, NSUs, BSAs, a Triumph Twin engined ice sled, and one of the last projects was a Norton engined dragster with a Druin Compressor.... that didnt work...and another compressor..... that didnt work....

 
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o0norton0o said:
I'd like to order a set of those beads,... but until they get here...

I have a galvanic reaction question as well. I have CBR600 fork dampers installed in my commando. I turn down and thread the fork cap nuts to fit the commando forks, so it's bare aluminum and steel. I've looked at the galvanic metals chart and that combination isn't highly galvanic at all, so without the presence of an electrolitic liquid, it would almost certainly not be an issue.

Wtbs, I was thinking about doing an "at home" hard anodize to strengthen the aluminum threads a bit, being that 20 TPI is such a fine thread. Anyone here do an at home hard anodize to anything threaded??


** Steve, Is mazak the same as Zamak? The gears on my lathe are made of zamak. So far they are ok, but they have a reputation for being crap....
Click to expand...
I’ve run bare alloy fork top nuts for years without issue (standard on Maxton fork conversions). I’ve been using a thin smear of silicone grease and all is good.

There’s no harm in anodising if you so wish, but it’s not strictly necessary.
 
concours said:

CNC Controls

Mazak set a precedent in CNC development with the introduction of our MAZATROL programming language in 1981. And, over the last three decades, we’ve continued to improve upon this programming language.
www.mazakusa.com
Click to expand...

ZAMAK (or Zamac, formerly trademarked as MAZAK[1]) is a family of alloys with a base metal of zinc and alloying elements of aluminium, magnesium, and copper.

Ha ha,... ok, kind of funny that it's both names and the same thing
 
Fast Eddie said:
I’ve run bare alloy fork top nuts for years without issue (standard on Maxton fork conversions). I’ve been using a thin smear of silicone grease and all is good.

There’s no harm in anodising if you so wish, but it’s not strictly necessary.
Click to expand...

When I first made them I wondered about galvanic reaction turning the fine threads to dust. The metal interactive chart says that it's highly unlikely because of the metals involved and the lack of an electrolitic fluid to enable the decay, but that also got me looking at maybe hard anodizing those fine threads just to harden them up a bit. I'm still thinking about doing it "at home" just to see if it helps. I have made a few sets of fork caps and the first set I made is both rough threads and on the lose side of the thread spec, so hard anodizing it would tighten up the thread contact with the fork tube and smooth the threads out a bit. that's a Win/Win situation, so I was wondering if anyone here had home anodized threads before just to get a heads up on my possible results...

Thanks Nigel
 
Worry about galvanic corrosion no more.

www.thingiverse.com

norton commando 850 by Lemoine19

pour les rayons de la roue , il faut les imprimer et les tordre legerement pour leur donner une inclinaison puis les coller sur un cote de la jante , mettre le moyeu et repeter l operation pour le cote oppose .Toutes les pieces du model sont collees , je n ai pas forcement prevu d attache...
www.thingiverse.com www.thingiverse.com

Galvanic corrosion ?


Just change to worrying about yield and tensile strengths.
 
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