×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Best way to remove galvanizing from mild steel

Best way to remove galvanizing from mild steel

Best way to remove galvanizing from mild steel

(OP)
Hi

Could anybody perhaps shed some light on what is the correct procedure to follow to remove existing galvanizing from mild steel so as to have it properly re-galvanized?

Thanks

RE: Best way to remove galvanizing from mild steel

Ask your galvanizer. In lieu of that, 30-50% Hydrochloric works.

RE: Best way to remove galvanizing from mild steel

(OP)
Ok, thanks very much.

RE: Best way to remove galvanizing from mild steel

We do small batches of stripping with Muriatic acid that we buy at the local hardware/plumbing supply.  It's basically hydrochloric acid.  Does a very nice job of it.  You need to be careful though, the byproduct is hydrogen gas, which can provide some additional entertainment, provided we're outdoors.  I would have to officially recommend that you let your plater do this, however.

RE: Best way to remove galvanizing from mild steel

Heating to red hot removes it, but may create other problems like distortion and evolution of toxic gas.

Why remove it before hand. If it is dipped in molten zinc, the original coating should melt and mix with the bath.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Best way to remove galvanizing from mild steel

I also need to know how to remove old galvanizing from a steel angle in a transmission tower.  Sometimes a car hits one of our towers and we have to replace a leg member.  They would like to weld in a new piece but I am reluctant to let them weld on the old leg.  A bucket of acid 30 feet in the air is not a great idea so can they grind off the galvanizing?

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Best way to remove galvanizing from mild steel

patprimmer.
"Why remove it before hand. If it is dipped in molten zinc, the original coating should melt and mix with the bath."

   Sometimes the reason for removing Galvanised before re coating is because the metal was not properly prepped before dipping. The resultant coating does not adhere very well to the parent metal and peels later.
      Re dipping does not cure that problem.
B.E.  

RE: Best way to remove galvanizing from mild steel

Patprimmer,

welding over zinc can lead to liquid metal embrtllement, as the zinc will penetrate in the metal in the haz.
Seen this in a case where they forgot to normalize a zinc-plated object prior to galvanizing, and decided to do this afterwards.
The hydrochloric acid, with the necessary precautions, would do the trick, but personnaly I would have it done by a more experienced company because of the health risks involved.

RE: Best way to remove galvanizing from mild steel

For welding insitu, if it's thin gal over thick metal, I normally weld over it and you can see it burn away about 1/2" ahead of the weld. If the gal is thick or the metal thin, I would grind first to do it insitu.

If it could be dismantled, for welding I might treat with inhibited hydrochloric acid and or grind the area, depending on quality requirements and size of job and size of weld and stress on the joint.

The OP does not specify why it if faulty, but if the problem was actually faulty pretreatment,then obviously a pickling/proper pretreatment process would be better.  

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Best way to remove galvanizing from mild steel

There are "spray on" galvanizers that claim they work..  No experience but have been sold for years.

RE: Best way to remove galvanizing from mild steel

Thanks for the tips.  I'm feeling much better about welding in the field but I still want to specify that they grind off the zinc before welding so they don't burn the zinc into fumes and get sick.  The guy in the field can't afford to lose too many IQ points. ;)

_____________________________________
I have been called "A storehouse of worthless information" many times.

RE: Best way to remove galvanizing from mild steel

There's also a rod produced by Cronatron (although they were recently bought out by Lawson), I can't remember the number on it, but it's designed for welding galvanized. We've used it on a number of bridge jobs and had very pleasing results compared to just using a plain 7018 like Lincoln Excalibur or others.
 

RE: Best way to remove galvanizing from mild steel

I also think you can get welders masks with filters or respirators for welding over zinc.

You can do local repairs at the weld by wiping the weld with a rod of zinc while the area is still hot enough to melt the zinc, but not hot enough to burn it. A poorer treatment is zinc rich paint.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources