Pipe ID Surface Corrosion due to Rain Water

[PlumbingBoy]

Hello all,

First of all, I'm new here, so please excuse me if I made some mistakes. Secondly, I have a little problem that those of you with corrosion background might be able to help.

Background : a bunch of pipes sitting around in a yard, stored/stacked horizontally uncovered. Rain and snow get to them and while the OD surface is coated, the ID surface is not.

I need to figure out the amount of rust that's formed over a period of time. So, I managed to find data on atmospheric corrosion rates for different locations throughout USA, but I'm wondering if there is any data on how to predict the corrosion rate for the pipe ID ends due to rain and/or snow. I figure probably about 1-1.5 ft deep into the pipe and about bottom half of the pipes are exposed to rain/snow.

Anyone knows how to predict the rate of corrosion for this area ? Or maybe leads as to where I can find relevant information ? Any help is appreciated. Thank you.

Tom Wahjudi

 

[Metalguy]

Why not simple take a few samples and measure the depth/amount of corrosion? Are you a student?

 

[unclesyd]

Since you are coating the O.D. why not throw in a Vapor Phase Iinhibitor and use readily available end caps/covers.

 

[PlumbingBoy]

Metalguy,
The client wants a theoretical number also. They are sending me a sample pipe so I can do rust collection to find out how much rust has been formed for a certain amount of pipe. No, I'm not a student.


unclesyd,
The problem stemmed from the fact that the pipes have been sitting around in a yard/lot for 4 years and the client wants me to predict how much rust they will have to remove from all the pipes before using them. You are absolutely correct that they should have done preventive measures before letting hundred of miles worth of pipes sitting around in a yard.

 

[odle1128]

Forget the theory, have a metallurgy lab cut some of the pipes open and examine them.

Robert Odle

 

[quadswift]

Well done odle1128. I like your style.

Quick visual after you have got the results and then cut off the ends and you can the sell the stuff!

Cutting off a couple of feet (what are the typical lengths, 6m randoms?)is probably cheaper than examining every pipe and doing remedial work.

And make sure that the next lot are covered / protected!

Regards,
Quadswift

 

[ramharsh]

Obviously client need to ensure that rusted/pitted pipe is meeting the design requirement prior to permitting for use. The thickness of scaling/amount of loose rust collected canot be correlated to the maximum reduction in material thickness.

Due to the oxidation the thickness of the scaling is much more than the reduction in material thickness and amount of rust/loose scale collected need can not reflect the maximum reduction in thickness of the material locally. (Corrosion need not be uniform throughout the length and there may be local pitting too).

In view of the above to enable convince the client that the pipe wall thickness is meeting the requirement, the following is suggested and it is the normal construction industry practice to ensure that the rusting/pitting is with in acceptable limits.

1) each length of the pipe need to be measured by digital thickness measurement along the length of the pipe, to cover the radial arc where the rusting/pitting is anticipated.
2)once the lowest thickness measured in a pipe length meet the minimum design thickness, those pipes can be acceptable.
3)while concluding the minimum acceptable thickness, the negative manufacturing tolerance applicable for the pipe grade may be considered (-12.5% / -10% as applicable).The pipes normally have 5 to 10% positive tolerance.
4)Here we shall note that the pitted area will have accelerated corrosion in service unless remidial measures are taken.