TSA Field Joint
07-28-2011, 06:02 PM,
#1
TSA Field Joint
Hi All,

I am working on a project in which pipe is coated with factory applied Glass flake epoxy. There is a requirement to coat 2 meters of the pipe end with TSA. could someone advise the best way to deal with the interface between TSA and GFE.

Can TSA be sprayed directly onto the GFE overlapping the free edge by say 50mm and then over coated with aluminium silicone sealer
Or
Is it better to butt up to the GFE free edge with TSA and overlap silicon sealer onto the GFE by 50 -100mm?
Not sure is GFE and aluminium sealer are compatible.

Any suggestions or advice will be welcome,
not the application is for subsea component, and will be protected by CP.

Many thanks
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07-29-2011, 01:22 PM,
#2
RE: TSA Field Joint
Hi OGMT

Sign0016 to the Surface Engineering Forum.

In an ideal world I think overlapping the thermal spray aluminium (TSA) coating with the Glass flake epoxy (GFE) would be best.

Overlapping the coatings I think would be better than butting them against each other. The TSA may be ok over the GFE but you will need to prepare the GFE surface with grit blasting to get a reasonable key. I would suggest a bit of experimentation.

Does the customer not have specifications/procedures for this already?
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07-29-2011, 01:43 PM,
#3
RE: TSA Field Joint
The glass flake epoxy should be applied over the aluminum. The GFE will probably be electrically insulative, so it will prevent the cathodic protection of the aluminum in this configuration. In order for the aluminum to provide corrosion protection, it must be in contact with the base metal. Also, the aluminum must bond to the base metal so it does not peel off.
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07-29-2011, 03:28 PM,
#4
RE: TSA Field Joint
Djewell is correct in what he has said. In addition, I have seen instances where the heat from aluminum application is enough to degrade and fail the epoxy (it depends mostly on the quality/temperature resistance of the resin used). Moreover, the silicone sealer may prevent proper adhesion of the epoxy. In a perfect world the aluminum is applied first, then the epoxy, then the sealer. Since I am aware that the world we live in is not perfect, I would recommend informing your customer that the ideal method for application is as described above, but that since pieces have been epoxy coated before arriving at your facility your can make a clean termination at the edge of the epoxy and apply the aluminum and sealer in that fashion. In theory the galvanic action of the aluminum should adequately protect the steel at the joining of the 2 coating systems.
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07-29-2011, 07:04 PM,
#5
RE: TSA Field Joint
Hi djewell

Not sure I understand what you are getting at here

(07-29-2011, 01:43 PM)djewell Wrote: The GFE will probably be electrically insulative, so it will prevent the cathodic protection of the aluminum in this configuration. In order for the aluminum to provide corrosion protection, it must be in contact with the base metal.

Surely cathodic protection is provided for the steel alone. There is nothing in this system that could possibly provide cathodic protection of the aluminium.

From my point of view the TSA is there to protect the steel substrate, partly by cathodic protection. The aluminium coating will be in contact with the steel except for a small overlap around the interface where the two coatings meet.

Wait a moment, re-read everything Rolleyes If what you meant is a situation where the aluminium coating only covers the GFE with no contact with steel substrate, then yes that would be pointless and I assume you meant it will prevent the cathodic protection of the steel by the aluminium in this configuration. Sorry, probably being a bit pedantic.

May be misinterpretation of OGMT's original question. I assumed 2m of pipe end would be bare or have GFE coating removed before TSA and that the question was what to do at the interface of two coatings.

Hi OGMT

Maybe butt the two coatings as best as you can and coat interface region with GFE.

Is the reason for TSA because of high temperatures at the end of the pipe i.e. too high for the epoxy?

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07-29-2011, 07:49 PM,
#6
RE: TSA Field Joint
My comments were meant as you understood them the second time. The aluminum is intended to provide cathodic protection to the steel. Applying it over epoxy would be a waste of effort and material because aluminum will only protect when it contacts the steel.
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