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Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 6:58 AM

I have coated a CS Pipe with APCS 1A( Epoxy TopCoat ) coating System. This piping is going inside a concrete surface. Will this Paint affects the concrete or do concrete affects the Paint. Need some clarification on this issue. If anyone have reference standards. It would be much appreciated.

Thanks,

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#1

Re: Coating of Steel Pipes coming in a Concrete Surface

02/15/2016 7:59 AM

Some phone calls are needed:

  • To the suppliers of the pipe
  • To the suppliers of the concrete
  • To the suppliers of the paint.

Get going. Don't waste time waiting here!

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#2

Re: Coating of Steel Pipes coming in a Concrete Surface

02/15/2016 9:14 AM

To repeat PWSlack's simple instructions:

Some phone calls are needed:

  • To the suppliers of the pipe
  • To the suppliers of the concrete
  • To the suppliers of the paint.

Get going. Don't waste time waiting here!

Otherwise look at the paint specs on the internet.

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#3

Re: Coating of Steel Pipes coming in a Concrete Surface

02/15/2016 9:35 AM

Concrete interiors, next to the pipe, are very alkaline and caustic at time of installation. That means it will have large numbers of assorted ions, mainly Calcium and Sodium in the wet matrix. These might decline with time, with the proper concrete formulation? The epoxy will allow some travel of these ions through to the metal, where the CS will begin to corrode - in a few isolated spots at first. This corrosion will spread along the pipe and will do two things. In time it will eat through the pipe, and, since the oxidation products of steel increase in volume, will compress the pipe and expand the concrete in an irresistible way - who knows what will fail first?? I have seen concrete breaks many inches thick due to this. The use of zinc rich silicone or epoxy that is formulated to resist the alkaline is what I suggest over pipe that has been prepared to receive it. Galvanized pipe and fittings makes sense here.

So if you want this to be a long lasting job, make requests of the same people others have suggested as well as these

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#4

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 10:23 AM

I don't think it's ever a good idea to run steel pipe in concrete without some sort of sleeve....Depending on what is running inside the pipe, it could be dangerous....

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#5

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 2:38 PM

Would it not have been prudent to ask this question prior to coating the pipe with something that may be incompatible and which, in this case, definitely is incompatible?

APCS 1A is a grading for general purpose primers for atmospheric applications only, and is normally only for use in the pH 6 to 9 range.

You need to go to grade 9 or 10 before you can even consider concrete immersion, and then you would need to be very - very careful that the coating was not damaged either during installation of the pipe or pouring of the concrete. Much safer to go with a plastic coated pipe, or slip it through a larger plastic tube.

If you must use this particular pipe, and failure is to be avoided, then consider cathodic protection as a stop gap, but the coating will eventually fail due to the pH of the environment.

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#6
In reply to #5

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 6:24 PM

If, and this is a big if, the paint was mixed properly and applied properly, over a properly prepared metal according to the application specifications, there should be no problems using it.

Given the country of application, and the lack of apparent materials knowledge of the OP, there is doubt about the final product's ultimate performance.

Product Data Sheet

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#7
In reply to #6

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 7:43 PM

I notice that they say nothing about moisture permeability - which is the enemy of steel embedded in concrete. Any chloride ions present make things worse.

A few of these links will show this

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#10
In reply to #7

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/16/2016 12:08 AM

And yet, Corrosion of Embedded Materials - Portland Cement ...says this,

"Although steel's natural tendency is to undergo corrosion reactions, the alkaline environment of concrete (pH of 12 to 13) provides steel with corrosion protection. At the high pH, a thin oxide layer forms on the steel and prevents metal atoms from dissolving. This passive film does not actually stop corrosion; it reduces the corrosion rate to an insignificant level. For steel in concrete, the passive corrosion rate is typically 0.1 ┬Ám per year. Without the passive film, the steel would corrode at rates at least 1,000 times higher (ACI222 2001)."

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#12
In reply to #10

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/17/2016 11:04 AM

That's right, in practice steel reinforcement in concrete works OK, as long as correct cover is provided.

To get back to steel pipe in concrete, it depends on the details. Steel puddle pipes set in concrete walls usually have a flange in the middle, to locate it longitudinally and give a longer leakage path. The flange and about 100mm either side are left uncoated, so for a wall say 300mm thick the coating ends 50mm into the wall. The bare steel bonds very well to the concrete, just like re-bars.

A length of coated pipe set in a wall would be less rigid and likely to leak. Wrapping in a plastic sleeve would be worse.

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#8
In reply to #6

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 8:31 PM

There is absolutely NOTHING OT about that statement.

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#13
In reply to #8

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/17/2016 1:49 PM

Agree, without reservation.

I think someone may have seen your link to the Product Data Sheet, and not realized that your posting of it was part of an on-going string of related posts.

Casper71

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#9
In reply to #5

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/15/2016 11:53 PM

Having seen (and many year ago poured) concrete being poured, I'd say it's not unreasonable for the paint to be nicked, if only by the aggregate, hence the sleeve or cathodic protection recommended by other posters.

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#11

Re: Coating of Steel Pipes Coming in a Concrete Surface

02/16/2016 6:34 AM

Clarification: Just carry on and do it. Another contractor will fix it later with a quick fix. No worry.

Standard: That be standard in all industries.

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