Corrosion Resistance Testing

The approved method of testing of fireclay brick for corrosion resistance to electrolyte is the standard ISO 20292 [182]. The hole is drilled in the brick, or it is preformed in a castable, then the electrolyte is poured in the hole, and the brick is placed in the furnace. After the exposure, the brick is cut, so that the change to the square of the hole may be measured. The degree of corrosion is calculated in the surface of corrosion. The lower the square of corrosion is, the more corrosion-resistant the material will be (Fig. 2.78). 

The variation of the cup corrosion test is [183] in using the graphite crucible for electrolyte. The porosity of the graphite crucible may vary. The graphite crucible is placed on a refractory layer. In this type of test, the sodium vapor is taken into account. If the porosity of the graphite crucible is 12-14 %, the result depicts the interaction of refractory with sodium, which moves in graphite. If the porosity of graphite is 28 %, the result depicts the interaction due to the capillary movement of 

2 Refractories and Carbon Cathode Materials for Aluminium Reduction Cells 

Siljan [187] has found a good correlation between the corrosion resistance in a cup cryolite corrosion test and the depth of cryolite infiltration. A 220-kA reductitm cell was lined with eight different alumina silica refractory materials and switched off for investigation of refractory conditions after 500 days. The results proved the good correlation. However, it appears that it is not a strict correlation from a physicochemical point of view between the interaction during hours and the kinetics of penetration of the melt within many months. 

It has been stated [187] that there is a good agreement between the corrosion resistance (cup cryolite resistance test, 24 h, 950 °C) and the silica content in alumina silica refractory. In the beginning of the process, a silica-rich layer appears that plays the role of a protective layer. Rather often the segregation of the melt on the silica reach and fluoride reach parts takes place (Fig. 2.79). Usually, the cup cryolite resistance of refractories increases as the porosity decreases. 

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Corrosion-resistance test This can be done with the help of a salt spray test. The test piece is suspended in a salt spray chamber (Figure A13.6) for. seven days in 100% relative humidity (IS 101 and IS 11864). After the test, the surface should have no signs of deterioration or corrosion. 

Corrosion resistance testing of ceramics is detailed in the literature.44,45... 

Corrosion resistance tests were carried out in accordance with the ASTM D1654 requirements using the following aggressive media 30% sulfuric acid, 20% hydrochloric acid, or 30% potassium hydroxide. Coating samples were kept in this media for 250 hours at 40°C, and were then subjected to tensile load tests. The results of the tests are shown in Table 5.4. 

At lesser rubber levels, heavy duty solventless coatings models based on dlethylenetrlamlne or fatty polyamide cures, showed elastomer-modification (10 phr rubber level) to advantage in Gardner impact, mandrel bend and corrosion-resistance testing (41). Impact testing (direct and reverse) gave 110 and 60 in-lbs, respectively for the rubber-modified fatty polyamide cured epoxy coating (14 days at R.T.), whereas a control formulation tested 10 in-lbs in each mode. 

The dissolution of material into an aqueous solution and so on, has a merit as well as a demerit to the enviroimient. Consider coated materials for an example. One of the objectives of a surface treatment such as plating is to improve corrosion resistance. In this case, it is preferable that the materials do not dissolve in water. This improvement of corrosion resistance enables the long-term use of materials, and will contribute to the reduction of resources and energy required for materials production. In Japan, JIS (Japanese Industrial Standards) H8502 (1999) regulates the methods of corrosion resistance tests for metallic coatings so as to evaluate the corrosion of a material. This standard includes the ISO 4540 (1980), ISO 4541 (1978) and others. 

For the biocompatibility and bioadhesion tests similar restrictions as in the corrosion resistance tests must be observed. A comparison of the behaviour of the different materials is possible only if the testing conditions are identical. Results obtained in animal experiments with rats and rabbits must be treated with reservations because both animals show intense bone growth and rapid healing after the implantation. 

Keywords Stillwater Mining Company, Ca-ferritic slag. Magnesia-chromite bricks. Rotary kiln. Corrosion resistance test. Refractories, RHl... 

Corrosion resistance tests were performed with ground samples in a Huey Corrosion Tester for seven days. The above values are averages of duplicate runs. Solution strengths were calculated on a weight basis and strengths were maintained by replacing with new solutions each day. 

The immersed tests are usually produced in big crucibles, filled with at least one corrosive agent. The dimension of the tested rods (usually rectangular bars) is 25 mm x 25 mm x 100 mm or 10 mm x 10 mm x 150 mm (Fig. 1.33). The bars may rotate or be dipped and pulled out or may be tested without rotation. The corrosion resistance tests for silicon carbide side lining materials are discussed in detail in Chap. 2. The corrosion resistance tests for A1 melt are discussed in Chap. 3. The tests for sodium swelling of carbon materials are discussed in Chap. 2, devoted to the lining materials for electrolysis, rather than in the chapter devoted to corrosion resistance. 

Fig. 2.73 (a) Laboratoiy reduction cell fOT the SINTEF corrosion resistance test to bath and aluminium and the samples (b) after testing [150]... 

Corrosion Resistance Tests for Bath and Molten Aluminium... 

Improving high temperature corrosion resistance Test programme... 

In response to the above-mentioned severe corrosive environments, the development and application of new CRMs and CRCs, corrosion resistance testing and evaluation methods, and methods for the analysis of corrosive environments have been advanced, as shown in Fig. 19.4 and described below. 

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