Materials Performance

DEC 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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13 NACE INTERNATIONAL: VOL. 53, NO. 12 MATERIALS PERFORMANCE DECEMBER 2014 Editor's Note: Additional MP Blog items appear in the individual technical sections: cathodic & anodic protection (p. 38), coatings & linings (p. 46), and chemical treatment (p. 58). More than 3,000 corrosion professionals from all over the world participate on the NACE International Corrosion Network and NACE Coatings Network. You can post your question and receive expert advice in a matter of minutes. To join either or both of these free list servers, go to the NACE Web site: nace.org, click on the "Corrosion Central" link, and then "Online Corrosion Community List Servers." The networks look forward to your participation! f ittings. Some drill holes in the pipe. Some use a collar that vents at the f langes. I would expect to see the same behav- ior from HF. The method used to create a PTFE liner really impacts the physical properties of the material when it comes to permeation. Basically, the thicker the better. A: As far as I am aware, the concen- trated HF supplied to laborato- ries comes in 2.25-L or 500-mL containers made from high-density polyethylene or poly propylene. While PTFE may well be suitable for HF transport and storage, it does seem to be an expensive option. Internal corrosion of gas piping Q: Does anyone have experience in monitoring the corrosion rate of pipelines transporting clean, sweet natural gas (methane-ethane 97%) having the following contaminants? • Carbon dioxide (CO 2 ): <2.5% • Hydrogen sulfde (H 2 S): <10 mg/m 3 • Total sulfur: <110 mg/m 3 • Water (H 2 O): <95 mg/m 3 • R-SH: <6.0 mg/m 3 • O 2 : <0.1% What is the corrosion rate range expected in mpy at this gas contaminant level? Is there any standard or public document indicating mpy ranges accept- able for my gas pipeline? A: I worked for fve years monitoring internal corrosion rates in a gas pipeline with similar gas quality, and at the end we decided to stop the program because we realized that internal corro- sion wasn't a meaningful threat to the pipe. We just monitor composition to be sure that the gas quality does not change: the corrosion rates we measured were below 0.1 mpy with gravimetric coupons (changed in a three- and six-month schedule).

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