Pressurized corrosion tests

High-Temperature and High-Pressure Corrosion Testing... 

During this phase of the life of the aircraft, missiles, and equipment, it may be assumed that these items will be transported by truck, rail, airplane, or ship. These methods of transport will expose the hardware to high and low temperatures, high and low humidity, rain/hail, sand/dust, salt fog, temporary immersion, and reduced pressure. Corrosion tests to simulate shipping/transportation can be designed but usually are deferred to the more severe operational environmental tests. 

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

Deflagration Arrester Testing For end-of-line and tank vent flame arresters, approval agencies may require manufacturers to provide users with data for flow capacity at operating pressures, proof of success during an endurance burn or continuous flame test, evidence of flashback test results (for end-of-hne arresters) or explosion test results (for in-line or tank vent arrester applications), hydrauhc pressure test results, and results of a corrosion test. 

Bishop, C. R., Corrosion Tests at Elevated Temperatures and Pressures , Corrosion, 19 No. 9, Sept., 308t-314t (1963)... 

Owing to their simplicity, measurements with the hydrogen sensors are easily automated. Figure 30 shows a setup in which eight hydrogen contact cells are used in an investigation with a steel pipe filled with a corrosive test medium underpressure. Temperature, pressure, and hydro-... 

Corrosion detection plays an important role in any corrosion control program. Most of the methods employ nondestructive test methods and include hydrogen evaluation, radiography, dynamic pressure, corrosion probes, strain gauges and eddy current measurements. Of these, the methods employed in cooling tower practice are hydrogen evaluation and corrosion probes. 

Tamper-proof seals are added to discourage unauthorized or undetected field adjustments. Once testing is complete, a metal identification tag (of soft lead, which is easy to imprint, yet impervious to corrosion) is attached to the SRV. The tag records the location number, set pressure, and test date. 

The attack at a pressure of 240 bar is very severe at temperatures between 300 and 390 °C where the local gradient is steep. In the steady state section at 400 °C, the bite is comparatively moderate. Further corrosion tests indicate that at higher pressures the bite speeds up and that a higher steady state operating temperature has a minor influence on the corrosion rate. 

The latest corrosion experiments were performed with reactors made of alloy 625 and Titanium. The reactors in form of pressure tubes are used as samples. Since titanium does not own the required mechanical strength for high temperature - high pressure applications, it is used in form of liners for the corrosion tests. The length of... 

The national pressure vessel codes and standards require that all pressure vessels be subjected to a pressure test to prove the integrity of the finished vessel (ASME BPV Code Sec. VIIID. 1 Part UG-99). A hydraulic test is normally carried out, but a pneumatic test can be substituted under circumstances where the use of a liquid for testing is not practical. Hydraulic tests are safer because only a small amoimt of energy is stored in the compressed liquid. A standard pressure test is used when the required thickness of the vessel parts can be calculated in accordance with the particular code or standard. The vessel is tested at a pressure 30% above the design pressure. The test pressure is adjusted to allow for the difference in strength of the vessel material at the test temperature compared with the design temperature, and for any corrosion allowance. 

Corrosion tests have inevitable limitations in their capacities to mimic actual service conditions of equipment. Standard, ambient pressure, immersion test procedures, with intermittent fluid refreshment, are available for both metallic and nonmetallic materials, but are limited to the ambient pressure boiling point of the fluid, and provide limited scope to simulate the effects of stress, geometry, heat transfer, and fluid flow. Such fesf procedures can be conducted at plant pressures and temperatures in autoclaves, and can be upgraded to focus on specific factors such as fluid flow and heat transfer. Even so a laboratory test, however elaborate, is a poor substitute for a test in the plant itself. 

As may be seen from Table I, concentrations of SO2 in the atmosphere are subjected to considerable variations. Moreover, SO2 concentrations used in corrosion tests are larger by several orders of magnitude. Therefore, it becomes highly questionable whether data obtained at high SO2 concentration levels may be also applied to practical exposure conditions. SO2 permeabilities of a series of polymer films like polyethylene, polycarbonate. polyamide 2 gg well as polyacrylate and cellulose triacetate have been shown to depend on SO2 pressure, especially at higher SO2 concentration levels. In the case of organic coatings such data are not available. It is therefore recommended to study SO2 permeability at low SO2 concentrations comparable to practical exposure conditions. 

The vaponr pressure of the solid was determined by mass-loss effusion from a nickel cell, from 1055 to 1297 K. Corrosion tests showed neghgible reaction between Ni and TI1F4, even in the molten state. In one ran, the effusate was collected on a tanta-Inm cyhnder and was fonnd to be TI1F4, by chemical and X-ray analysis. 

The pressurized blister test is an excellent method to combine electrochemical reactions at polymer/metal interfaces with a mechanical load. It allows the application of a mechanical stress from a homogeneously pressurized electrolyte on the adhesive/metal interface in a sample geometry that is accessible for the HR-SKP [28]. Depending on the adjusted conditions, information on the synergy of mechanical stresses, elastic or inelastic deformations of the adhesive, transport processes, and corrosive reactions could be obtained with this method. 

Deposition effects of rare earth oxides on the surfaee of iron and stainless steels have also been reported [58]. The eorrosion rate eonstants decreased significantly by the coating in corrosion tests under isothermal eonditions. In thermal cyclic conditions, protective scale spallation completely disappeared for eoated samples. The rare earth effect is more remarkable with elements located on the left part of the lanthanide series (lighter rare earths). For example, eeria coatings strongly modify the microstructure and texture of the wustite (FeO) scale formed during low pressure oxidation of pure iron [59]. Cerium is located in the wustite matrix as a CeFeOs phase which dissolves in FeO in time. 

Nasr-El-Din et al. (2002) have also investigated the corrosion inhibition of some aldehyde-based sulfide-snppression chemicals on steel conpons in a corrosion autoclave in acidic media. Formaldehyde was mentioned in the research, bnt other aldehyde-based chemicals were only tagged Aldehyde A, Aldehyde and so forth. Combinations of some of these aldehyde-based chemicals were also investigated. They condncted the tests at 0.5 mol% H2S with varying concentrations of sulfide scavengers at ambient, 150°F, and 275°F conditions of temperatures and at pressures of 3000 and 5000 psi. All the corrosion tests were completed at 4 h contact time. They concluded that all the chemicals are effective to some extent in controlling H2S and in corrosion inhibition. 

As unfired pressure vessels, stills will need biennial inspections, but if it is believed that corrosion may have taken place a prompt check should be made. If a process whose moderate corrosion has been predicted on the basis of laboratory results is due to be done on the plant, corrosion test coupons should be installed in the plant and inspected regularly. 

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