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Re: Dissimilar Metals

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SEE UBC STANDARDS - MECHANICAL CONNECTIONS & CONTACT
WITH DISSIMILAR MATERIALS.
Hope this Helps.

djk

On Thu, 8 Aug 2002 16:34:40 -0700 "vicpeng" <vicpeng(--nospam--at)telus.net> writes:
> If available "electrolyte" cannot get through, around, or connect, 
> the gasket/pad, I wouldn't expect there to be any significant 
> "arc-ing", or galvanic activity.  If the connection is expose to 
> weather etc, possible electrolytic paths would be a concern.  
> Otherwise, any required distance will probably be a function of the 
> resistivity of the gasket/pad.
> 
> I don't know the chemistry of "separated" metals where there is no 
> path.  Potentials may well be set up that affect the interaction of 
> those very metals to other adjacent objects.
> 
> You might want to ensure there is sufficient "edge" distance as 
> well.  
> 
> Thor A Tandy  P.Eng, MIPENZ
> Victoria BC
> Canada
> e-mail: vicpeng(--nospam--at)telus.net
> 
> ----- Original Message ----- 
> From: CanitzCF(--nospam--at)aol.com 
> To: seaint(--nospam--at)seaint.org 
> Sent: Thursday, August 08, 2002 4:14 PM
> Subject: Dissimilar Metals
> 
> 
> To All -
>   I have a situation where, via a bolted connection, an aluminum 
> vertical 
> plate is attached to a steel shear tab located along the web of of 
> steel 
> channel. I specified a 1/2" thick closed cell neoprene pad (plus 
> S.S. bolts) 
> between the aluminum plate and the shear tab. Is there a rule of 
> thumb or 
> guidance regarding the minimum separation distance between 
> dissimilar 
> materials? I know in similar cases, the aluminum plate could be 
> coated with 
> an asphaltic paint where it abuts the shear tab so perhaps no 
> minimum 
> separation is required. I'm concerned that should the pad be too 
> thin 
> galvanic action could arc between the two metals.
> 
> TIA,
> Charlie Canitz, PE
> Bel Air, MD 



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