Example of pitting after corrosion testing in accordance with ASTM G48 Method A . The test temperature of 22 °C is too aggressive for lean duplex grades such. Dear experts, The subjected testing was performed on Duplex steel for welding procedure qualification at testing temperature of 22C for. Abstract ASTM G48 – “Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride.
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Register now while it’s still free! Close this window and log in. Are you an Engineering professional? By joining you are opting in to receive e-mail. Promoting, selling, recruiting, coursework and thesis posting is forbidden. Dear experts, The subjected testing was performed on Duplex steel for welding procedure qualification at testing temperature of 22C for suggested time period of 72 hours as per ASTM G48 using Method A.
The testing medium was acidified FeCl solution. The sample was pickled and prepared but still could not meet the client requirements no pitting or crevice corrosion in either weld metal or HAZ is permitted and failed in testing twice.
Could any one explain the potential reasons for the failure and moreover what countermeasures shall be considered to avoid repeated failure?
First of all, if you were using scidified ferric chloride it was method C. Secondly, have you done an A test?
Where you cut a sample and grind the surfaces, no pickle or passivation allowed, and test in ferric chloride? This should indicate if you have any intermetallic phases present. Or at least do micros. Are you sure that the temp is correct for the alloy? Are you working with a cast duplex product?
G48 Method A is commonly called out for cast superduplex stainless with a 24 hour test period at 50C and 24hrs. Otherwise, for wrought it normally would revert to A for testing. If testing protocol isn’t the problem I would look at composition and solution treatment for answers. The product is wrought duplex but testing to G48 using Method A is client specification requirement for welding procedure qualification at 22C for suggested 72 hours.
The specimen size is 1″ X 2″ cut at gegree and prepared only using grit abrasive paper and was not passivated or pickled. The acceptance criteria, no pitting or crevice corrosion either at weld metal or HAZ is permitted, is mentioned only in client specification. You did not add HCl to the test solution did you? Practice A does not use acid. Is the pipe pickled? Then after cutting you should pickle the sample. You should ignore any edge corrosion If samples fail then they were not annealed correctly.
Perhaps not at temp long enough or not cooled quickly enough. Yes, we did not add HCL to the test solution.
We hired an independant 3rd party to perform corrosion testing to G48 Method A as per client requirements but by mistake 3rd party booked the specimen to A and testing was done also to A and result is OK. Client is not accepting the results and require to perform the testing to G48 Method A for 72 hours.
Please advise, is it acceptable if we may submit TQ to client to lower the testing time to 24 hours instead of 72 hours for normal duplex wrought specimen because G48 is flexible on timings and suggests 72 hours although variations may also be used. Hi Syed, Passing G48A test is always a challenge to welding engineers. Many Upstream Oil gas specifications allow 24 hrs of testing duration for such test see extrats as below: Exposure time shall be 24 hours. All surfaces shall be exposed. The sides only may be ground to a grit finish and the edges may be rounded.
Samples shall not be pickled or passivated prior to test. Should the clients’ insistence is for 72 hrs duration then: If the results for BM and consumables are satisfactory then only pursue 72 hrs test for weld coupons.
If you’re forced to pursue the wrost case scenario, then the other option is to use super duplex welding consumables for the weld coupon. Pradip, and All Don’t confuse G48 and A They use similar test solutions but they are done for very different reasons. There is not one single test that will accomplish both. Don’t play mix and match with test conditions and procedures.
The purpose of A is to detect intermetallic phases. All sample surfaces must be freshly ground with no further treatment. G48 is looking to determine the resistance to the initiation of chloride pitting.
You may polish the edges, if the finished product is pickled then you can pickle, the times and temps are general guidance. If someone has a specific procedure that they want reproduced then that is the way it is to be done. metbod
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Ed, The issue is not confused. This test methkd does not determine the critical pitting temperature or test for the suitability for use in a particular environment. This test method is designed solely for detection of the precipitation of detrimental intermetallic phases in duplex stainless steels.
G48 A method is designed to determine the relative pitting resistance of stainless steels and nickel-base, chromium bearing alloys. If alloy consistently fails at the above specified testing regime, assuming that metallurgical factors are not contributors then the ways to get around it on GA test would be: A aastm from 24 Deg C to 20 Deg C could be helpful.
However all tests have to be documented, results to be assessed by client and fabricators, with the Maximum Engineering Integrity of the q being the prime criteria. The oil and gas industry has spent a great deal of time and effort since the 80s in arriving at a standardised G48 test for duplex.
Unfortunately, if the client wants a 72 hour test, that is their prerogative. I don’t know any end users who test for 72 hours. If you have a generally sound wps. Overmatched metthod etc and you have good micros and impacts then the test is probably just too severe.
A good suggestion earlier methos to test the base metal this will demonstrate if you have any chance of passing. C tests at that temperature is ast, that the microstructure have been affected. Furthermore did you notice the presence of pits scattered on the entire surface of specimens or they are localized for example in the HAZ region?
Are the specimens with or without PWHT? Red Flag This Post Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.
ASTM G48 Method A-Corrosive Testing #4
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