Corrosion on steel members - Need your opinnion

[850R]

Hello all,

I'd like to get some opinions on this.

If the flange thickness of a wide flange section is 1”, and you specify that the corrosion is 0.25”.

Would you think that the flange is now 0.5” (Assuming corrosion on each side of flange is 0.25”), or 0.75” (Assuming corrosion on each side of flange is 0.25/2)?

Thanks in advance.

 

[bridgebuster]

It could be either or something else. It depends on the exposure conditions. I've inspected 100"s of bridges and have come across members that had corrosion on one surface and all surfaces.

 

[Gumpmaster]

Corrosion rates I've used for design in the past have been for each surface, so you'd loose 0.50" total. You'd also loose that on your web.

This is a pretty high corrosion rate. I had a similar corrosion rate on A36 steel in pH2 acid at 100C.

You probably need to get a corrosion specialist involved. Maybe cathodic protection or stainless steel shapes are in order.

 

[SlideRuleEra]

You don't mention how the steel is used, that is important. My experience with bridges is the same as bridgebuster's.

Corrosion on electric generating station coal railcar unloader steel, exposed to both coal and weather, was bad everywhere except the bottom of horizontal surfaces. Here, coal dust collection is minimal and the surface is protected from the weather.

Inside these coal fired stations, corrosion was uniform, especially where the steel was routinely exposed to process or washdown water.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[850R]

Thank you very much for all the input. The steel is used for offshore structures.

 

[JStephen]

If you specify that the corrosion is 0.25" without saying any more, you've just left it very vague, and subject to exactly this kind of issue.
In some cases, corrosion is understood to be each surface.
In other cases, it is understood to be added to the thickness.
If you don't say which, and in the absence of any code or standard to clarify, you've kind of left it open.