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FRP Compatibility with chemically treated water

FRP Compatibility with chemically treated water

(OP)
I have corrosion issues with currently installed galvanized steel components (railing, beams, etc.). I am trying to figure out the best material to replace the existing items with. I am pretty set on FRP, but am not sure if there may be a better material for the application. Any insight is appreciated. I have attached a photo of the corrosion (after 5 years in service) and some water analysis for review.



RE: FRP Compatibility with chemically treated water

The picture shows the corrosion occurred in the local railing between the dry and wet sections. Is it correct?
Applying an epoxy coating to protect the galvanized steel locally may be an option too.

RE: FRP Compatibility with chemically treated water

(OP)
The entire railing in the wet section is losing the galvanization. There are areas in the wet section that are just as bad as the one pictured.

RE: FRP Compatibility with chemically treated water

Were all of these sections galvanized after they were fabricated?
Was heavy Zn application used?

I suspect that the answer to both is NO.
Going to FRP should work well.
But so would properly made, galvanized, and sealed metal parts.

FPR is not nearly as stiff as metal, so dimensions will need to be much larger or everything will feel 'bouncy and flexible' even if it can carry the loads.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: FRP Compatibility with chemically treated water

(OP)
They appear that they were galvanized after fabrication, however, this tower was installed long before I worked here, so I can't confirm what was actually done.

I believe part of the issue is the chemicals we inject into the water (Sodium Hypochlorite, Sodium Bromide, Sulfuric Acid, etc). This gets on the metal with the spray and eats it up.

RE: FRP Compatibility with chemically treated water

The chemistry that you provided is not very corrosive.
But wet/dry cycling or near the interface is aggressive even with good water.

I presume that you are controlling to a 'scale index' target of some sort.
And adding some inhibitors and biocides. Fairly standard stuff.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: FRP Compatibility with chemically treated water

Can the water be kept away from the railing and walkway?
It could be a safety issue as the staffs walk on the slippery walkway and contact with the water with unwanted chemicals.

RE: FRP Compatibility with chemically treated water

(OP)
It would be tough to keep water away from the railing without blocking airflow to the tower. The grating it highly slip resistant, doesn't get very wet, and is not frequently traversed, so there is no issue there.

RE: FRP Compatibility with chemically treated water

What is the grating fabricated from? The grating looks to be in good condition.

RE: FRP Compatibility with chemically treated water

(OP)
It's FRP.

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