Immersion testing simple tests

Diffusion rates for liquids in an elastomer are easily measured by absorption (immersion) testing, a simple process as indicated in Figure 23.6. An initially weighed immersed sheet sample of elastomer is removed from the liquid periodically, rapidly dabbed with tissue paper, reweighed, and replaced. A plot of mass increase versus root time is drawn (also see Figure 23.6), root time being chosen due to the form of appropriate solutions of Fick s laws. 

Experimental CFTs were determined by Brigham and Tozer in three different ways based on chloride solutions two electrochemical and one chemical. In electrochemical testing in sodium chloride (NaCl) solution, the methods involved recording the current while either increasing the potential at suitable selected temperatures (apotentiodynamic test) or increasing the temperature at suitable fixed potentials (a potentiostatic test). Alternatively, a potential was established by the redox couple (Fe(in)/Fe(n) in a simple immersion test in ferric chloride solution. 

In order to evaluate the contraction behavior of the candidate liner material when coupled to a laminate composite, a simple immersion test was performed on selected samples. The specimens were immersed in a liquid-hydrogen bath for 45 min upon removal they were subjected to a qualitative examination, for cracks, color change, etc. All films tested reacted favorably except the aluminized Mylar, which developed cracks in the aluminum upon flexing, and Kynar, which was very brittle and cracked without external load. Contraction properties of various materials are shown in Fig. 3. 

In chromizing, the ultimate chromium concentration that can be obtained is 100% (i.e., chromium metal). It could therefore be useful to consider the corrosion resistance of such a material. Wesley has carried out simple immersion tests in acids, alkalis, and salt solntions, and also under... 

The other testing methods mentioned in Table 7.41 are simple immersion tests carried out at elevated temperature, most often in boiling solution. Established norms... 

The reaction mechanisms by which the alloy elements influence the rate of corrosion of weathering steel are not precisely known. While the presence of alloy elements improves the corrosion resistance of a carbon steel subjected to humidity cycles, during a simple immersion test weathering steel and carbon steel yield... 

While many laboratory tests for resistance of metals to stress corrosion cracking have been developed, only a few tests are amenable to actual in-situ testing in seawater. These primarily consist of the exposure of statically stressed type test specimens such as described in ASTM G 30, G 38, G 39, and ISO 7539-2, ISO 7539-3, and ISO 7539-5. In addition, welded specimens such as described in ASTM G 58 are excellent for evaluation of the stress corrosion resistance of weldments in simple immersion tests. Evaluation of corrosion fatigue is usually limited to laboratory testing. 

Laboratory tests to determine the behavior of materials and corrosivity of automotive fluids such as engine coolants, engine oils, automatic transmission fluids, and fuels involve exposure to the actual fluid as close to operating conditions as possible. In most cases, aging of the fluids due to their functional use produces a more corrosive liquid therefore it is important that the test be conducted on used liquids or that aging of the fluid occur in-situ. Simple immersion tests can be used if chemical and physical environmental effects are introduced. This is not always possible and therefore simulated service tests have been developed. These laboratory bench tests simulate more... 

A laboratory immersion test for corrosion in hydraulic brake line fluid is described in Motor Vehicle Brake Fluid SAE J1703. This test includes the use of standard metal coupons for mass change and visual examination after immersion at 100°C in the brake fluid. Other tests are used to evaluate specific components in the braking system such as that described in SAE J1047 for hydraulic brake line tubing. Internal corrosion is not considered as important as external corrosion of the braking system and therefore only simple tests are used outside of on vehicle service tests. 

The simplest type of laboratory test corrsists of exposing coupons to the liquid phase only. Simple immersion tests are performed using some form of glassware, such as a flask or a resin kettle, and a condenser for refluxing. A typical setup is a 1000-mL flask containing 500 mL of liquid. Laboratory coupon testing is described in ASTM G31 [16],... 

T] = E-Eq. a semi-logarithmic Tafel plot yields the lines of the current densities of anodic metal dissolution and cathodic reduction of the redox system, as presented for iron dissolution in 0.5 M H2SO4 in Fig. 1-30 (Kaesche, 1979). The intersection of both lines yields Er and the related corrosion current density 4 within the electrolyte. In the case of iron corrosion in sulfuric acid, the corrosion rates determined by the electrochemical evaluation of the Tafel plot and the chemical analysis of the dissolved species or the weight loss of the specimen for simple immersion tests agree sufficiently well (Kaesche, 1979). 

General immersion tests General immersion tests can be as simple as the standard saltwater immersion test for coatings to be used in the atmosphere, or as complicated as cold wall effect immersion tests for heavy coatings to be used constantly in immersion service. It is essential to reproduce the anticipated conditions of the field exposure as dosely as possible when evaluating coatings for immersion service. 

Acetic Acid 10 214 101 G - - E immersed, comparison of heat transfer cortditions with simple immersion test. Corrodent renewed every 48 hrs., total time 95 hrs. 

Simple immersion tests. Basically, small sections of the candidate material are exposed to the test medium for a period of time and the loss of weight of the material is measured. Immersion testing... 

J Q Corrosion behavior of mico/alumlnum com- posiles in 3.5% NoCI at 25 °C (75 T). (a) Weight-Joss data from simple immersion tests. b) Corrosion rates calculated from the weight-loss data shown in (a). Source Ref 18... 

Small scale test runs prior to preparative irradiation experiments may be carried out in tubes which are either taped to the lamp housings (immersion wells) depicted in Figures 13-1 and 13-2 or placed in turntable reactors ( merry-go-rounds ). These arrangements permit the simultaneous irradiation of several samples, but only a fraction of the available light emission is used. In Figure 13-4 a simple reactor is shown which focusses almost all the emitted light into one sample which can be scaled up also to semi-preparative volumes. In this way the necessary irradiation time can be reduced sharply. 

Laboratory tests used in the development of inhibitors can be of various types and are often associated with a particular laboratory. Thus, in one case simple test specimens, either alone or as bimetallic couples, are immersed in inhibited solutions in a relatively simple apparatus, as illustrated in Fig. 19.34. Sometimes the test may involve heat transfer, and a simple test arrangement is shown in Fig. 19.35. Tests of these types have been described in the literatureHowever, national standards also exist for this type of test approach. BSl and ASTM documents describe laboratory test procedures and in some cases provide recommended pass or fail criteria (BS 5117 Part 2 Section 2.2 1985 BS 6580 1985 ASTM 01384 1987). Laboratory testing may involve a recirculating rig test in which the intention is to assess the performance of an inhibited coolant in the simulated flow conditions of an engine cooling system. Although test procedures have been developed (BS 5177 Part 2 Section 2.3 1985 ASTM 02570 1985), problems of reproducibility and repeatability exist, and it is difficult to quote numerical pass or fail criteria. 

Figure 4.50. Cumulative dissolution results. Two experimental tablet formulations were tested against each other in a dissolution test in which tablets are immersed in a stirred aqueous medium (number of tablets, constructional details and operation of apparatus, and amount of medium are givens). Eighty or more percent of the drug in either formulation is set free within 10 minutes. The slow terminal release displayed by formulation B could point towards an unwanted drug/excipient interaction. The vertical bars indicate ymean - with Sy 3%. A simple linear/exponential model was used to approximate the data for the strength 2 formulation. Strengths I and 3 are not depicted but look very similar.

To simulate service conditions tests may be needed with exposure being on one side of the test piece only, which can achieved by using a simple jig in which the test piece forms one end of a cylindrical container. If immersion under pressure is needed a special jig would have to be developed. The standard does not include cases of partial immersion nor immersion under pressure. 

A common chemical laboratory test for corrosion resistance is a simple exposure test using metal coupons. The ASTM standard G48 —Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution—describes a simple exposure test. The material coupons (e.g., 60 x 60 mm) are placed on a glass cradle and immersed in the solution in such a way that the coupons are evenly exposed. 

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