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Join Date: Dec 2011
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Treatment for Sea Water Intake Pumphouse Concrete Structures

11/21/2015 8:06 AM

We are taking the water Directly from Sea for our water treatment plant and cooling towers through Sea water intake pumphouse, at this pumphouse we are used epoxy coated steel and acrylic paints on walls but still it is getting corrosion, pl suggest what to do

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#1

Re: treatment for sea water intake pumphouse concrete structures

11/21/2015 9:40 AM

"

  • Fluoropolymer- resin/lubricant blends that offer excellent corrosion protection
  • Xylan®- a fluoropolymer that can extend component life
  • Molybdenum Disulfide- friction protection for high pressure loads
  • Epoxy, air dry- cost-effective, corrosion resistant coating
  • Epoxy, thermal cure- excellent impact resistance, plus corrosion and abrasion resistance
  • Phenolic- ideal in low pH, high temperature environments
  • Phosphate- ferrous metal coating for anti galling and minor corrosion resistance
  • Polyurethane- high gloss topcoat for epoxy and inorganic zinc
  • Inorganic Zinc- corrosion and weathering protection for steel
  • PTFE- the original non-stick coating, able to withstand high temperatures
  • PPS/Ryton®- thin film chemical resistant coating
  • FEP- PTFE characteristics with better abrasion resistance
  • PVDF/Dykor®- high quality coating ideal for chemical processing applications
  • ECTFE/Halar®- resistant to most chemicals plus high impact strength
  • Ceramic Epoxy Coating- a unique abrasion resistant coating that protects by binding ceramic particles to a resin system"

http://www.metcoat.com/corrosion-resistant-coatings.htm

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#2

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/21/2015 3:46 PM

Use something that is compatible with seawater instead! Come on, Mildred. You need to know how to search the internet for materials compatibility. I'm not going to do it for you, because that might make you lazy, and neither of us wants that now, do we?

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#3

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/21/2015 10:30 PM

Hire a corrosion engineer. He may suggest impressed current protection in addition to what others above have suggested. What have you implemented to protect the pumps and piping?

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#4

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/22/2015 2:19 AM

Don't let the seawater get on the walls.

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#5

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/22/2015 9:37 AM

I've seen this time and again, in bridge decks, but not necessarily seawater pump stations. Both deal with the corrosive effects of Chloride ions attacking the reinforcing steel and other ferrous embedding products and constructs.

Usually corrosion occurs within epoxy-coated rebars due to improper handling and practices during construction.

Sometimes epoxy-coated rebar is mishandled, starting during transport from the manufacturing plant all the way to the job site, as well as mishandling by the Iron Workers placing it, which results in nicked and/or cracked epoxy coating.

Also, the end of the rebar where it's been cut, at the fabricator and/or in the filed, don't receive a filed-applied coating of epoxy on the exposed steel.

You need to incorporate an integral hydrophobic (water-repelling) admixture in the concrete mix. To date, nothing is a 100% foolproof, because even if such admixture are utilized, they cannot provide "absolute" protection against intrusion, especially on the atomic level. Also, they cannot provide intrusion protection at cracks in the concrete.....the admixture cannot "bridge" the crack.

You need to provide a dense, cement and pozzolan (Fly Ash) rich concrete mix. I'm talking about using a mixture with no less than 680#of cement per cubic yard, with a pozzolan substitution for cement is the range of 17% or more (by weight). You need to conduct laboratory testing of any proposed concrete mix.

You need to exercise all available means of minimizing concrete shrinkage cracking, including micro-cracking, with all necessary means and construction techniques during the concrete curing process.

By all means, conduct hydrostatic leakage testing per ANSI/AWWA D115-95 Standard and ACI 350.1 Standard.

Utilize a PROVEN surface coating that is acceptable at minimizing water absorption, especially chloride ion absorption. Keep in mind that concrete by it's very nature and composition, is a porous material and that whatever materials, means, and method that you incorporate in the concrete work will not prevent ALL absorption

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#6

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/22/2015 10:39 AM
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#7

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/22/2015 2:19 PM

In addition to epoxy coated steel ribbar protection there are four other additional procedures you may use to considerably retard and in some cases stop electrolytic degradation: A) Use a reverse electrolysis counter current device which reverses the spurious grounding plane electrical potential differences between the steel reinforcement bars and the sodium chloride chemical electrolytic action on the metal. There is a company which sells this power supply, but you will have to measure the electrolytic current yourself or pay them to do it. B) Connect all steel parts together with Cadweld bonds and ground at least at eight instances with a No.2-Cu conductors connected to at least four ⅝" Dia.x8ft. long Ground bars. Bury all ground bars 4Ft. under the ground or sea level floor. C) When casting the concrete walls, use PVC bonding fibers (usually one bag per CuYd of concrete) to increase cast concrete bonding integrity. D) Throughly cover-impregnate-paint the exposed concrete surfaces to prevent concrete from breathing the exterior saline atmosphere. You see, the rusting or corroding process of metals is, in reality, an electrical or electrolytic process which occurs when current flows (because of potential differences between ground plane and metal structures) from the ground to metals not properly grounded.It also occurs in metal to metal, because of the same phenomenon. To solve the problem. the current flow has to be neutralized. In boats, the problem is usually solved by mounting a sacrificial Zinc anode on the propeller shaft to counteract the cathodic action of sea water to metal metal parts. Speaking of which, and as a last preventive measure, you may also use four Zinc anode spherical elements on the Cu conductor drops to the ground bars. These will have to be inspected and changed periodically since they will corrode with time.

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#8

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/23/2015 6:31 AM

You might like to investigate "DENSO" protective processes for the metalic surfaces.

Denso (this is a specific trade name, but there are other alternatives available) is applied in layers, initially a grease smeared to cover the surface needing protection, then an impregnated tape (bandage) is fitted over that and finally a plastic tape is applied over that to mechanically protect the treatment.

It works this way. The grease creates a waterproof seal of the metal surface. Whatever O2 or corrosive elements are present (against the metal surface) quickly neatralise creating insignificant localised "tarnish" and the reaction stops.

We use this for Ductile iron pipe joints under tidal influence, fasteners, fittings and pipe joints in acid sulfate soils and so on.

The process is also widely used to protect piles and dock instalations and (I've heard) can also be applied underwater by divers.

The concern with most epoxy coatings and such is that they harden to a brittle finish that can then chip off locally.

I've witnessed 40 year old joints dismantled and the threads on high tensile (Not stainless) bolts once loosened were undone by hand along the orignial thread.

As for the walls, I'm presuming that is cladding of some sort. Change to fibre-glass, or some other plastic material for the cladding.

Sometimes it's just that the prevailing environment determines the useful life of the product.

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#9

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/23/2015 10:40 AM

Are you sure what you are seeing is corrosion or is it just salt crystal(s) buildup on the surface from precipitation?

The only way to control salt buildup on wall and equipment surfaces is to adopt a regularly executed cleaning maintenance program that will keep the buildup to a minimum and/or non-threatening level.

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#10

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/24/2015 8:24 PM

Were the interior walls and steel dry when the original coating of paint was applied?

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#11

Re: Treatment for Sea Water Intake Pumphouse Concrete Structures

11/27/2015 7:03 PM

Perhaps you are also having chloride attacking and damaging the concrete itself, exposing the steel more readily. The better approach is to use a different type of portland cement, specifically the sulfate-resistant type V. Type 1 is widely used (almost ubiquitous) and poor in resistance to salt water, while type V is harder to find but quite good in resistance to salt water. This has been known for decades, but is often overlooked.

--JMM

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