Corrosion sampling

Three factors influence the rate of corrosion of metals—moisture, type of pollutant, and temperature. A study by Hudson (1) confirms these three factors. Steel samples were exposed for 1 year at 20 locations throughout the world. Samples at dry or cold locations had the lowest rate of corrosion, samples in the tropics and marine environments were intermediate, and samples in polluted industrial locations had the highest rate of corrosion. Corrosion values at an industrial site in England were 100 times higher than those found in an arid African location. 

Ohpvctii. ns, lests Vessels. Relief Devices, Corrosion Sampling Facilities ... 

FIG. 25-4 Corrosion racks used to expose corrosion samples in operating production equipment (a) inside pipes (b) inside process vessels (c) to be bolted onto baffles and brackets with process vessels. 

Side stream sampling devices can be used to collect biofilm and corrosion samples. The biofilm, inorganic passive layers, and metal attacked samples can be characterized with scanning electron microscopy and energy dispersive... 

Storage at 4 °C or less is recommended for all samples, and storage at —20 °C or less is recommended for crude and processed extracts. The recommended containers are amber glass bottles with Teflon tops, but Teflon containers may be used for particularly corrosive samples. Stainless steel containers are not considered acceptable because of the potential for sample contamination. Additional research to address optimum storage conditions (temperature, time, and storage containers) that preserve sample integrity is recommended. This study should include research on the storage of raw samples, crude extracts, and processed extracts. 

Figure 3 Typical quartz plasma torch positioned within a (induction) load coil. The center (injector) tube can be made of quartz or inert materials (alumina, platinum, or sapphire) to allow corrosive samples (including those containing hydrofluoric acid) to be introduced into the plasma. One-piece quartz torches, torches with demountable injector tubes, or completely demountable tubes are used.

The increase in cathodic kinetics due to the action of biofilms on passive alloy surfaces can also increase the propagation rate of galvanic corrosion. Potentiodynamic polarization studies show that cathodic kinetics are increased during biofilm formation on passive alloy surfaces. Tests on crevice corrosion samples of passive alloys S30400 and S31600 revealed that crevice initiation times were reduced when natural marine biofilms were allowed to form on the exposed external cathode surface. (Dexter)5... 

The sample holders in (fc)-(m) are used in Linseis DTA equipment. In (k), removable sleeves made of metal or ceramic are used to contain the sample. This type of sample holder is convenient for cleaning purposes as the sleeve may be easily removed, leaving the exposed sample. A disadvantage of this type of sample holder is that the thermocouple is in direct contact with the sample and may be attacked by corrosive sample materials, thus changing its EMF output characteristics. A similar disadvantage is present for the probe-type sample holders in (/) and C/i). in which the thermocouple is immersed in the interior of the sample. The glass sample container in tei is usually a disposable capillary tube I -2 mm in diameter. A sample holder for horizontal use is illustrated in Iml. 

Ion-Selective Field Effect Transistors. Ion-selective field effect transistors (ISFETs) are semiconductor devices related to the solid-state detectors used in spectroscopy (discussed in Chapter 5). In this case, the surface of the transistor is covered with silicon nitride, which adsorbs H ions from the sample solution. The degree of adsorption is a function of the pH of the sample solution and the adsorption of H" " ions results in a change in the conductivity of the ISEET channel. The cell requires an external reference electrode. ISEET pH sensors can be made extremely small (about 2 mm ) and are extremely rugged, unlike the fragile glass bulb pH electrode. They have rapid response times and can operate in corrosive samples, slurries, and even wet solids such as food products. The sensor can be scrubbed clean with a toothbrush, stored in a dry condition, and does not require hydrating... 

Retrieve and analyze refractory and checker corrosion samples from the TCR regenerators... 

In exposure tests in the tidal and immersion zone of the natural North Sea waters off Helgoland, the 18% chromium steel X2CrMoTil8-2 (SAE 444, 1.4521) was attacked by pitting and crevice corrosion despite its molybdenum content. The superferritic steels X 1 CrMo 26 1 (DIN-Mat. No. 1.4131) and XlCrNiMoNb28-4-2 (25-4-4,1.4575), on the other hand, remained free of pitting corrosion. Slight crevice corrosion was observed only in the steel X 1 CrMo 26 1 under washers. In special crevice corrosion samples, crevice corrosion occurred under washers made of both PVC and austenitic steel X2CrNiMoN17-13-5 (SAE 317 LMN, 1.4439) [99]. 

Using special crevice corrosion samples that simulate the conditions of washers, the crevice corrosion behaviour of the 36 wrought alloys and 9 corresponding cast alloys made of molybdeniferous stainless steels and nickel-based materials listed in Table 45 were tested in filtered natural seawater at 303 K (30 °C) [179]. 

An equivalent evaluation also resulted from the analysis of exposure tests with crevice corrosion samples made of the relevant alloys after 90 days in stagnant seawater at 303 K (30 C) [180]. 

There are also other sources of radiation at nuclear power plants, such as neutron startup sources, corrosion samples, in-core and ex-core detectors, calibration sources for instruments and sources that are used for radiographic inspections. 

ICP-MS Besides the plasma torch and sample introduction supplies, ICP-MS requires consumables that are situated inside the mass spectrometer. The first area is the interface region between the plasma and the mass spectrometer, which contains the sampler and skimmer cones. These are traditionally made of nickel, which is recommended for most matrices, or platinum for highly corrosive samples and organic matrices. A set of nickel cones costs 700-1000, whereas a set of platinum cones costs about 3000-4000. Two sets of nickel cones and perhaps one set of platinum cones would be required per year. The other major consumable in ICP-MS is the detector, which has a lifetime of approximately 1 year, and costs about 1200-1800. Some systems also have a replaceable ion lens. It is suggested that five of these at 100 each are required for a routine laboratory. When all these are added together with the torch, the sample introduction components, and the vacuum pump consumables, investing in ICP-MS supplies represents an annual cost of 9,000-11,000. 

By far the most common design used for ICP-MS is the pneumatic nebulizer, which uses mechanical forces of a gas flow (normally argon at a pressure of 20-30 psi) to generate the sample aerosol. Some of the most popular designs of pneumatic nebulizers include the concentric, microconcentric, microflow, and cross-flow. They are usually made from glass, but other nebulizer materials, such as various kinds of polymers, are becoming more popular, particularly for highly corrosive samples and specialized applications. 

In general, mild steel samples coated with polyaniline in hydrochloric acid exhibited better corrosion protection than those exposed in sodium chloride solution under the same coating conditions as indicated simply by comparison of Eoc and corr as shown in Figs. 31.11-31.13. Corrosion samples tested in this study for all seven conductive polymers can be classified into one of the above three categories. 

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