Weight loss test

Weight loss test using boiling alkali and glass pieces. 

Determination Test, Weight loss test, Eschke test, Salt spray test and Sulphur dioxide test at 50°C. Mechanism of inhibition of corrosion and surface study of mild steel was also studied by Metallurgical Resesarch Microscopy and Scanning electron Microscopy. 

By performing weight loss tests, technical personnel can estimate the corrosiveness of an environment over a period of time. If the corrosion rate is determined to be high, preventive measures can be taken to prolong the remaining life of the equipment. The preventive measures can include the addition of a corrosion inhibitor, a change in the process, an application of anticorrosion coatings, or the addition of a CP system. 

A conductive polymer film of polypyrrole doped with polymolybdate anions was electrodeposited onto steel and found to provide corrosion protection in neutral and acidic 3.5% NaCl solution [152]. The anodic codeposition of polypyrrole and Ti02 onto mild steel in an oxalic acid medium has been described [153,154]. The PPy and Ti02 composite showed a considerable improvement in anticorrosion properties with respect to PPy films in salt spray and weight-loss tests. It was suggested that these composite films could be applied as a primary coating replacement for the phosphatized layers on mild steel [154]. 

Specimens with step and dual structures do not drop grains in boiling acid tests, and therefore have acceptable or passing corrosion rates in weight-loss tests. Materials represented by such specimens can therefore be accepted for plant use on the basis of the 1.5 min oxalic acid etch test. Only those materials that have a ditch structure must be submitted for testing in the hot acid tests to determine whether or not their corrosion rates fall below or above the acceptance rate for the given alloy. 

Information on "acceptable and nonacceptable corrosion test results has been given for the two EPR tests in the section above on these tests. Acceptable etch structures (step, and in some cases, dual) are also identified for the oxalic acid etch test. The absence of fissures in bends after certain copper sulfate tests is considered an indication of acceptable results. However, in the case of weight-loss tests (nitric acid, ferric sulfate, and certain copper sulfate tests) the standard ASTM test methods merely show how corrosion rates are calculated without identification of rates which are evidence of the onset of susceptibihty to intergranular attack. 

Weight loss is the easiest and least expensive method since that method requires only test specimens, the solution, a container, and the appropriate environmental parameters. Weight loss tests can be conducted in low and low conductivity solutions, even in the atmosphere. An analytical balance is required for both before and after weight measurements. Multiple specimens must be used when evaluating the change in corrosion rate over time. Sp>eci-mens cannot be reused for corrosion rate versus time measurements after first exposed and cleaned because high initial corrosion rates will occur each time the specimen is used. This will lead to artificially high corrosion rate data. 

ASTM G 31 Standard Practice for Laboratory Immersion Corrosion Testing of Metals Describes procedures for conducting laboratoiy weight loss tests Provides information on reporting and factors to be aware of. 

FIG. 2—Typical Huey test apparatus with water-cooied condenser for conducting sample general corrosion (weight-loss) tests up to the solution boiiing point. Samples are typically suspended In the solution by Teflon string or glass rods. 

Corrosion in brownstock and post-oxygen washers has been investigated by Bennett and Magar [795] using electrochemical procedures. Their results showed that corrosion is affected by pH, chloride concentration, temperature, and aeration. These tests were complemented with instantaneous corrosion rate measurements by linear polarization resistance methods and by weight loss tests. 

Corrosion in mechanical pulping processes was investigated by Crowe [202] via weight loss tests and potentiody-namic polarization tests. Vapor phase condensate corrosion was more severe than liquid phase corrosion. 

Estes et al. [232] used electrodes to study the basicity of molten salt mixtures and performed weight loss tests that... 

Test materials and conditions for electrochemical and weight loss tests... 

Figs. 14(a)-(b), whose data were listed in Table 2, show Tn and Ipass vs. A1 content x plots, respectively. One can easily see that both bri and Ipass increase with x. This implies that the passive corrosion property of AbCoCrFeNi decreases with A1 content x. Fig. 14(c) shows Wioss vs. X plot. Like bri and Ipass, Wioss also increases with x. Notice that, unlike potentiodynamic polarization, immersion weight-loss test is a natural electrochemical reaction, i.e., without applying any voltage on the test sample. On the other hand, bn and... 

The thickness loss and weight loss tests were not conducted, due to the relatively small size of the electrodes. 

Aqueous corrosion is electrochemical in nature. It is therefore possible to measure corrosion rate by employing electrochemical techniques. Two methods based on electrochemical polarization are available The Tafel extrapolation and linear polarization. Electrochemical methods permit rapid and precise corrosion-rate measurement and may be used to measure corrosion rate in systems that cannot be visually inspected or subject to weight-loss tests. Measurement of the corrosion current while the corrosion potential is varied is possible with the apparatus shown in Figure 1.4. 

Various studies (Hinton et al. 1985, Hinton 1989) have shown that the rates of eorrosion of high strength Al alloys 2024 and 7075 (see table 1 for compositions), as determined by weight-loss tests, in quiescent 0.1 M NaCl solution, after 21 days immersion were reduced by the presence (in solution) of small concentrations of various R chlorides (figs. 3,4). 

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