Weight loss measurement

A characteristic of the corrosion on buried ferrous metals is that the attack is usually mostly in the form of pitting, especially with the cast irons. This raises a problem in measuring the extent of corrosion in burial trials. Usually both the weight loss, measuring the average loss of section, and the deepest pit, measuring the maximum loss of section, are reported. For assessing the severity of the attack on buried pipes, the second parameter is clearly the most important. 

Potential measurement This technique has provided valuable information as to the condition of passive/active materials, particularly in the chemical industryAlthough quantitative weight loss measurements are not obtained, measurements can be on-line and more importantly, can be monitored using the actual plant material in situ) as a sensor. 

As pointed out above, accumulatory pressure and weight loss measurements usually refer to the total reaction. When there are several volatile products, it is necessary to identify all components and investigate progressive changes in gas composition. Quantitative determinations of the amounts of each product (EGA) should, ideally, be combined with measurements of the total extent of reaction, although Gam [143] has recommended caution in the interpretation of results from simultaneous measurements. 

ENA was recently used for remote on-line corrosion monitoring of carbon steel electrodes in a test loop of a surge water tank at a gas storage field. An experimental design and system for remote ENA and collection of electrochemical impedance spectroscopy (EIS) data (Fig. 13) have been presented elsewhere. In the gas storage field, noise measurements were compared with electrode weight loss measurements. Noise resistance (R ) was defined as... 

A plot of mass loss versus time can provide information about changes in the conditions under which the test has been run. One example of such a plot comes from the ASTM Standard G96, Standard Guide. As mentioned previously, weight loss measurements are appropriate for measurement of localized pitting corrosion, including that caused by MIC. 

Electrochemical impedance, weight loss, and potentiodyne techniques can be used to determine the corrosion rates of carbon steel and the activities of both sulfate-reducing bacteria and acid-producing bacteria in a water injection field test. A study revealed that the corrosion rates determined by the potentiodyne technique did not correlate with the bacterial activity, but those obtained by electrochemical impedance spectroscopy (EIS) were comparable with the rates obtained by weight loss measurements [545]. 

In random degradation molecular mass decreases early, while in chain degradation the molecular mass of the polymer remains almost constant. Characterisation methods for molecular mass are thus very sensitive methods to follow random degradation. In contrast, as monomer is produced in chain depolymerisation, weight loss measurement techniques are the best methods to follow this kind of degradation. (Chapters 10-12, in Section IV, of this book focus on the methods used in the molecular characterisation and analysis of polymer degradation and polymer degradation mechanisms.)... 

TGA. Weight-loss measurements for the electrical-electronic grade novolac epoxy were reported in our earlier work. For samples heated in N2 to 350°C no differences attributable to the presence of FR were observed. Isothermal measurements indicated a 20% weight loss for the unfilled molding compound after 12-days at 220°C. 

TGA. Unlike the previous two sets of molding compounds, the semiconductor grade novolacs investigated in this section do not differ solely in the presence or absence of a flame retardant. However, they are considered to be relatively equivalent. Weight loss measurements for the FR formulation, sample F, and the non-FR compound, sample G, are presented in Figure 7 for both nitrogen and air. Several differences are observed in the weight loss curves for these samples. 

The major concern was the thermal oxidative stability performance of the new resin. Weight loss measurements at 250,285 and 300 °C provided comparable low values at 250 and 285 °C. However, at 300 °C, the B1 composite exhibited a marketly lower weight loss than PMR-15. The temperature capability of B1 composite is obvious from Fig. 41, where the flexural properties of resins are plotted as a function of the ageing time at 285 °C. PMR-15 seems to be a superior resin in this test. 

Weight losses measured during the transformation indicated that the two phases differed in their chemical composition. Assuming a MoS2 —> MoNx reaction, the x values were close to 1.2 and 1.0 for L-MoN and H-MoN respectively. Analysis of nitrogen and sulphur were again performed in a LECO analyser. N was determined as before, while S was detected as S02 by an infrared method. The results are reported in Table 13.9 as well as the density values measured in tetrachloromethane. 

In a later study by the Schmidt group (27), electron microscopy was used to characterize morphological changes in microspheres (<0.6 cm in diameter) of Pt, Rh, Pd, and Pt-Rh alloy in a number of reaction environments the reactions were ammonia oxidation, ammonia decomposition, and propane oxidation. No other experimental techniques, such as weight-loss measurements, were employed. After prolonged exposure to reaction mixtures of ammonia and air at temperatures less than 727°C, the surfaces of the spheres were reconstructed to favor specific crystal planes. The structure of the facets was found to be a function of the reaction mixture, temperature, and metal (Fig. 13). In the same reaction mixtures, as well as in pure ammonia at higher temperatures... 

Direct Weight Loss Measurement (method 1). In this method several containers were charged, each with 0.3 g of raw shale of known particle size and 50 ml of an HC1-KC1 solution with ionic strength of about 0.1 molar ions/1. and pH of 1.28. The reaction was allowed to progress after a specific period the shale from one of the containers was quickly separated from the acid by vacuum filtration and washed thoroughly with deionized water. The shale was then dried at 105 °C for at least 2 hr before weighing. The same process was repeated for a preweighted container, and the data were adjusted. 

Surface OH concentration can be inferred from weight-loss measurements made on samples with surface areas as low as 1 sq. meter per gram. However, the... 

Conventional weight loss measurements in testing inhibitors are time-consuming since measurable weight loss is required to obtain meaningful data on corrosion rates. In general the performance of corrosion inhibitors is expressed in terms of percentage inhibition. 

The corrosion resistance of steels in acids is represented by isocorrosion diagrams. The resistance to uniform or general corrosion in various acids and sodium hydroxide was determined by weight loss measurements over a period of 96 h and the resulting data are given in Table 4.12. 

---