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Re: Corrosion Protection

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Vijay:

I would recommend hot-dipped galvanizing.  That is normally what we do in minor corrosive industrial or marine applications.  As far as field repair of welds, there are several methods for touching up the damaged area. First, the area should be prepared by remove the galvanizing to allow for better electrode current flow and consistency making a better weld.  This will also prevent the welders from becoming sick from the toxic fumes emitted by the heated zinc compound.  After welding the area can either be coated with a "cold galv."(ie: zinc rich paint/primer) or thermo-galvanizing which uses a heated stick to apply a relatively thick coating of zinc.
The former being more economical, while the latter being more substantial.  In my experience galvanizing is a good type of protective coating.  Just keep in mind that there are limits on the size of pieces that can fit in the dip tank.  You may need to check with local galvanizes.  Also, the amount of heat used in the process can damage (warp) certain sensitive items.


Chase Thornton, PE
Structural Engineer
Liberty Engineering, P.C.
Phone: (757) 499-2791
Fax: (757) 499-7984
email:chase(--nospam--at)libertyeng.net





Vijay K. Patil wrote:
Dear Friends

What kind of corrosion protection for structural steel works is good and
economical
1. Galvanization
2. Epoxy coating
3. Polysulphide based chemicals

All the manufacturers claim that their method is the best claiming
drawbacks of the other
1. One cannot weld on galvanized surface as the zinc coating goes off
and in fact accelerates the corrosion process. Whereas the galvanizers
claim that there are sprays available with 94% zinc which when sprayed
on the welded surface would once again make it good against corrosion.

2. Epoxy is supposed to be non UV resistant and ofcourse bonding with
steel is not good esp. when the section is bent after application of
epoxy it cracks and after a few days starts peeling off.

3. Polysulphide(the magic potion) based chemical manufacturer claims
that it can be simply brush applied. However it has a soft surface which
can get scratched off. However the remedy is supposed to be simply apply
it again on it.

All manufacturers have tall claims and certificates proving their
product is good as compared to other.

What in your opinion is the best for protection against corrosion.

Vijay Patil



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