12-09-2008, 02:47 PM,
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Vijay Deshpande
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RE: TSA COATING
(12-01-2008, 10:55 AM)Stuart Milton Wrote: From the values you mention, I assume you are using Arc spray but please confirm.
Are you testing with a dolly on the job (e.g. bonded to the flat sheet for example) or have you prepared specific test dollies to use in a tester?
What is the coating thickness?
We are using Twin wire arc spray system using 1.6 mm wire. The test is carried out on job reference samples ( 400 mm X 400 mm 8 mm thick)and coating thickness is 150 to 200 microns.
Thanks and regards
Vijay Deshpande
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12-10-2008, 03:15 PM,
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Gordon
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RE: TSA COATING
Hi Vijay
I remember overseeing some operator approval/qualification testing, similar to what iwan-sedaryawan described above.
The basic requirements were:
Surface preparation roughness >85 - 130 Ry5 and >6 Ra
Coating thickness 225 - 400 micrometres
Adhesion test (ASTM C-633) >9 MPa
Adhesion test (ASTM D-4541) >7 MPa
Out of 5 operators, which all passed qualification:
The worst:
13 - 16 MPa (ASTM C-633) All coating failure
14 - 16 MPa (ASTM D-4541 using HATE tester) All coating failure
Even though this operator was well within the requirements for qualification, I thought he required more training/experience as his coating results were significantly poorer than the other operators.
The best:
25 - 27 MPa (ASTM C-633) Mix of adhesive and coating failure
13 - 23 MPa (ASTM D-4541 using HATE tester) All adhesive failure
With tests where adhesive failure occurred, actual maximum coating adhesion/bond strength can not be determined.
Grit blast preparation was using chilled iron grit (G12).
So to answer your question
Quote:Whats maximum achivable value for adhession test for TSA coatings.
I would say >25 MPa with good operators, good equipment/process/preparation and good testing equipment/adhesives.
Quote:We are getting values between 9 to 15 MPA with mechanical Dolly puller
If you are getting adhesive failures rather than coating failures, I would not be to concerned. If they are coating failures, then I think you could do better.
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12-20-2008, 12:52 AM,
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iwan-sedaryawan
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RE: TSA COATING
As per gordon says : adhesive failures rather than coating failures, pls check while you do the pull off test with dolly, it is in substate or between glue & dolly ? 70% successfully with maximum bonding strenth is depend on the preparation itself, check your grit blasting, presure etc, use roughness tester, surface comparator to achieve Sa 3 (white metal) surface cleanliness, I am sure you will get better bonding strength than before, based on our experience we can achieve more than 20MPa, around 25 MPa.
Having fun with TSA coating
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12-20-2008, 03:54 PM,
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Vijay Deshpande
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RE: TSA COATING
(12-20-2008, 12:52 AM)iwan-sedaryawan Wrote: As per gordon says : adhesive failures rather than coating failures, pls check while you do the pull off test with dolly, it is in substate or between glue & dolly ? 70% successfully with maximum bonding strenth is depend on the preparation itself, check your grit blasting, presure etc, use roughness tester, surface comparator to achieve Sa 3 (white metal) surface cleanliness, I am sure you will get better bonding strength than before, based on our experience we can achieve more than 20MPa, around 25 MPa.
Having fun with TSA coating
Most of the times its mix of glue and adhession failure. How ever we have not got a single cohesion failure
Regards
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10-11-2009, 03:03 PM,
(This post was last modified: 10-11-2009, 03:06 PM by markdavidson.)
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markdavidson
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Adhesion of flame spray TSA repaired with arc spray
I have some carbon steel equipment which has been flame spray TSA coated and has arrived at the fabrication yard with some damage. It will need repair but the yard TSA contractor only has arc spray equipment. The TSA contractor says it is unwise to repair using arc spray but is not clear why, some within our yard construction team believe it may be due to adhesion loss of the original flame spray TSA where it is overlapped by the repair arc spray. I am interested to hear of actual experience, does the overlapped flame spray lose adhesion?
Regards
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10-12-2009, 02:41 PM,
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Gordon
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RE: TSA COATING
Hi Markdavidson
to the Surface Engineering Forum.
Can only echo GlenB and Stuart Milton comments.
Can you give us an idea to the extent of the damage to the coating?
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10-13-2009, 08:37 AM,
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markdavidson
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RE: TSA COATING
Glenn/Stuart/Gordon,
Thanks for your responses. I have asked our coating inspectors at the yard to coordinate a trial by the TSA contractor, 1 set each of 3 dollies fixed to the (1) intact flame spray, (2) the arc overlap of the flame spray and (3) new arc spray to determine adhesion and provide some basis for future assessments and quieten the nay-sayers. The extent of defective coating is probably less than 5% of total area, distributed over the entire structure. Transportation damage is about 1-2%.
I'm hopeful that the yard superintendant will allow the trial to go ahead. In the meantime I've been advised that due to the construction schedule these items will be completely stripped and recoated by arc spray so they can be welded onto the particular topsides deck.
(10-12-2009, 02:41 PM)Gordon Wrote: Hi Markdavidson
:sign0016: to the Surface Engineering Forum.
Can only echo GlenB and Stuart Milton comments.
Can you give us an idea to the extent of the damage to the coating?
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10-13-2009, 03:02 PM,
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Gordon
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RE: TSA COATING
Hi Mark
Sounds like a worthwhile test to me, particularly if you are likely to face the prospect of needing patch repairs in future.
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