Coupon testing

The simplest form of compatibility test is to immerse standard ASTM coupons in a liquid or vapor in the lab. Coupons can be installed in the field in a stream. However making a coupon assembly for installation in a pipe or a vessel may be difficult and persuading plant operators even more so. Lab testing is easy to carry out but will not replicate real life conditions such as flow, agitation, stress (compression for gaskets) and one-sided exposure. For this reason, lab dunk tests are usually done for screening reasons. Application temperature is easy to achieve by space heaters. 

The coupons are weighed and dimensions carefully measured prior to exposure. Usually the solution is changed once a week and the test is carried out for a period of one month to six weeks. Often multiple coupons are used and some coupons re- 

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Choices of alternative materials. Corrosion probes are carefully chosen to be as close as possible to the alloy composition, heat treatment, and stress condition of the material that is being monitored. Care must be taken to ensure that the environment at the probe matches the service environment. Choices of other alloys or heat treatments and other conditions must be made by comparison. Laboratory testing or coupon testing in the process stream can be used to examine alternatives to the current material, but the probes and the monitors can only provide information about the conditions which are present during the test exposure and cannot extrapolate beyond those conditions. 

Coupon tests involved a number of metallurgies and were done to evaluate precipitator-plate alloys. Test stainless steel plates failed, not only because of pitting but also because stress-corrosion cracks developed. 

Guide for conducting corrosion coupon tests in plant equipment... 

The weep point or strain-to-first-crack in a wall for filament-wound pipe constructed using isophthalic plastic is currently found to be not less than 0.009 in./in. This has been repeatedly demonstrated by careful coupon testing and burst testing of pipes with strain gauge instrumentation attached. 

This series of three sequential MOC coupon tests used a hydrolysate surrogate and VX hydrolysate provided by the Assembled Chemical Weapons Assessment (ACWA) program. The VX hydrolysate used in the tests was higher in NaOH concentration and had higher trace amounts of chlorine and fluorine than the hydrolysate that will be produced from the NECDF stockpile. The goal of the three tests was to recommend MOCs for the SCWO reactor. Coupons made from a range of materials were exposed to representative SCWO conditions to determine corrosion rates and mechanisms. Because the amount of available VX hydrolysate was insufficient to support a test with a duration of 500 hours, one test with VX hydrolysate was run for 167 hours, and two tests with hydrolysate surrogate were run for 167 hours to expose the coupons to a total of 500 hours of operation. 

Ce in coupon tests with both GGW and brine about 10% of Se was removed for GGW only, and no uCo or 7Cs was removed. In the case of cerium, colloid coprecipitation with amorphous silica may explain these extraction results. The association of selenium with possible hydrated silicates is unknown. Further investigation of these associations will be required before any significance can be attached to these Na CO extraction results. 

This section will focus on explaining the electrochemical bases for two generic types of testing accelerated coupon testing and electrochemical testing. 

FIGURE 4.8 Side view of a Zr705 coupon tested in the static Bunsen separator acid for 450 h. 

Corrosion data of materials in HI, are extremely limited. The most comprehensive set is from Trester and Staley. Table 4.12 lists a summary of the immersion coupon test results from their work. The test temperature is similar to that for extractive... 

FIGURE 4.16 A Nb-lOHf coupon tested in a static HIx-H3P04 mixture at 140°C for 336 h new, post test, and post test with scale removed. 

FIGURE 4.20 C22-U-bend specimen coupon tested in the gaseous HI gaseous decomposition environment. 

FIGURE 4.21 C706 alloy coupons tested in cone. H3PO4 acid, cone. H3PO4 acid with a... 

Numerous material coupon test results have been collected over the years by researchers in the field of composites. To the best knowledge of the authors, there are two public databases containing test results specific to wind turbine composites. These are the FACT -database [3] and the database composed by the U.S. Department of Energy in collaboration with Montana State University (DOE/MSU)[4]. 

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