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Anonymous Poster

Electrolysis in Painted Steel Sheets

12/30/2010 4:07 AM

i erect pre-fab commercial buildings that have a metal framework that's enclosed with metal sheeting that's painted on both sides. these buildings are well designed for the most part. the major problem with these type of buildings is that the roof sheets corrode around the cadmium plated screws and rubber washers that holds the roof to a heavily painted [red oxide? steel framework. the sides don't seem to have this problem, though the method is identical. the cororsion is a fine grey powder that looks alot like battery corrosion. i contribribue it to electrolysis, though i'm not familar with the electrical aspect. that part is done my engineers and certified electrictions.

would a sacrafical metal between the building and ground solve the problem?
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34point5
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Join Date: May 2010
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#1

Re: electrolysis in painted steel sheets

12/30/2010 5:38 AM

No it would not - you are just paying the price of being irresponsible and "cheap"

Cadmium is a cumulative toxic metal and you endanger the bones of anyone using your roofs for water collection.

It is a sacrificial anode in this context, like zinc, but more active.

What you should do is use 'passivated zinc plated' fasteners with 'rubber washers' to attach roofing iron, be it galvanized or painted or bonded color.

And I would be passing that link on to the so called "engineers and certified electrictions".

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jlstitt2
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#3
In reply to #1

Re: electrolysis in painted steel sheets

12/30/2010 5:49 AM

thank's for the advice i don't design theses things. they're engineered. i just erect them. i'll try to pass this info on, but my experience with engineers is that they feel they know it all. i'ld love to get one out on the job site.
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mountk2
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Join Date: Jun 2010
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#2

Re: electrolysis in painted steel sheets

12/30/2010 5:43 AM

Rubber contains sulphur, use teflon (PTFE) washers. Try rivets in place of screws if that is admissible.

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jlstitt2
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#4
In reply to #2

Re: electrolysis in painted steel sheets

12/30/2010 5:56 AM

thanks, i've had great results using aluminum hucks [ large pop rivets] on aluminum sheets. i've never seen them called for on steel sheets.
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mountk2
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#6
In reply to #4

Re: electrolysis in painted steel sheets

12/30/2010 7:13 AM

As a matter fact besides aluminium alloys you can readily have steel rivets, I have at times used these with a rivet-gun conveniently on sea worthy steel containers.

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34point5
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Join Date: May 2010
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#5
In reply to #2

Re: electrolysis in painted steel sheets

12/30/2010 6:08 AM

If it was actually "rubber"

But even so, sulphur is a trace element and nutrient in plant matter - as is zinc

So why wait till someone comments then jump in and muddy the "don't poison folk" message?

And why suggest totally uneconomic, impractical and stupid ways of doing it?

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kramarat
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#7

Re: electrolysis in painted steel sheets

12/30/2010 8:28 AM

I have a prefab galvanized building on my property using zinc coated nuts and bolts as fasteners, I believe the washers are nylon or something similar. No problems after six years. I would switch to zinc plated fasteners.

For a definitive answer, ask milo, he's the resident metal expert.

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jlstitt2
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#8
In reply to #7

Re: electrolysis in painted steel sheets

12/30/2010 9:46 AM

thanks, who manufactured it. i know some people who would be interested in knowing.
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kramarat
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#9
In reply to #8

Re: electrolysis in painted steel sheets

12/30/2010 10:20 AM

This is the type of building I have. usbuildingsdirect.com. There are several different companies that sell these, but from what I understand only one company makes them.

These guys manufactured the fasteners, no problems whatsoever.

http://www.lelandindustries.com/

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