Mass loss tests

ASTM D 5537 Standard Test Method for Heat Release, Flame Spread, Smoke Obscuration, and Mass Loss Testing of Insulating Materials Contained in Electrical or Optical Fiber Cables When Burning in a Vertical Cable Tray Configuration... 

The simplest uniform corrosion tests are those based on coupon immersion and mass loss tests. The tests provide data on the uniform metallic corrosion rate most often expressed in English units as mils per year (mpy) or in metric units as millimeters per year (mm/y). While there are various standards for such tests, the predominant methods are those prescribed by ASTM G 1, "Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens. This standard contains a comprehensive reference list of other ASTM standards that also apply, depending on the type of tests of interest to the investigator. 

These mass loss tests consist of preparing metallic coupons, cleaning them before testing, weighing them before exposure, exposing them to the corrosive media, post-test removal of visible corrosion products, and reweighing. The corrosion rate is calculated from the mass loss measured, converted to a volume of metal loss by the material density, and finally to a corrosion rate by dividing this volume by the material surface area and the test time. 

Electrochemical tests are often preferred to mass loss studies as a method of measuring uniform corrosion. Such tests are preferred because in theory they (1) provide a realtime measurement of the metaUic corrosion rate, (2) can provide time-corrosion rate data on a single coupon, and (3) are rapid to perform. Disadvantages of the electrochemical tests include the requirements for comparatively expensive equipment (versus mass loss tests) and higher levels of technical expertise for data analysis. Fmthermore, the data reduction requires the use of conversion-"constants," factors applied to the results of the electrical measurements to convert the data to a corrosion rate. These constants ... 

Mass loss tests are a common means of testing many metals in atmospheric and submerged exposure. For steel in concrete they are destructive to the concrete and difficult to perform. Laboratory specimens typically have a portion of the embedded bar coated or taped to define a specific test area. These materials are often hard to remove and could gain or lose mass. Furthermore, at the initial stages of corrosion most of the damage is in pits which have relatively low mass loss relative to that lost in the formation of the passive film [12], and thus mass loss is not necessarily a good indicator of corrosion activity. 

A rather unique mass loss test method, ASTM G 67 (Test Method for Determining the Susceptibility of Intergranular Corrosion of 5xxx Series Aluminum Alloys by Mass Loss After Exposure to Nitric Acid [NAMLT Test]) has been developed to provide a quantitative measure of the intergranular susceptibility of 5xxx series Al-Mg and Al-Mg-Mn allo3rs. The technique is useful to determine whether material has become sensitized by exposure to elevated temperature. Development of the test is reported in Ref 23. 

Craig, H. L., Jr., Nitric Acid Mass Loss Test for the HI 16 and HI 17 Tempers of 5086 and 5456 Aluminum Alloys," Localized Corrosion—Cause of Metal Failure, ASTM STP 516, ASTM International, West Conshohocken, PA, 1972, pp. 17-37. 

Corrosion in white liquor has been studied extensively, but there is little information available on black liquor, aside from some work by Mueller [772], Wensley [124], and Singh [139,140], Mass loss tests in synthetic liquors containing inorganic and organic constituents of black liquors have been done at the University of Virginia [199],... 

Therefore, gravimetric and different calorimetric methods have been established to investigate stability and aging behavior of energetic compounds. " " Here, mass loss tests and the analysis by adiabatic and isothermal heat flow calorimetry are briefly described. 

Mass loss tests of solid energetic materials are carried out under isothermal conditions in precise temperature controlled furnaces. Usually, samples of 1-2 g are stored in special, open sample tubes at 75 °C or 90 °C for at least 18 days. During this period the sample mass is constantly recorded. A mass loss of >3% after 18 days at 90 °C is usually an indicator for restrictions in long-term stability. However, stability standards are only specified for specific energetic materials and compositions. For example, stable nitrocellulose-based propellants have to exhibit a mass loss of <2% after 18 days storage at 90 Mass loss data of energetic azides have been only rarely published so far. Only... 

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 Gmde. ... 

Anodes for boilers can be tested by such methods. Good-quality magnesium anodes have a mass loss rate per unit area < 30 g m d", corresponding to a current yield of >18% under galvanostatic anode loading of 50 /xA cm" in 10 M NaCl at 60°C. In 10 M NaCl at 60°C, the potential should not be more positive than t/jj = -0.9 V for the same polarization conditions [27],... 

Probably the most frequently made observation is the change in mass of a test-piece. This may take the form of a mass gain or a mass loss. 

Expression of mass loss in terms of a percentage of the original mass of a test-piece is usually meaningless except for comparing specimens of the same size and shape, since it does not take into account the important relationship between surface and mass. 

Since it is often difficult to visualise the extent of attack in terms of depth from such mass-loss units as mdd, it is common practice to convert these mdd figures into others to indicate depth of penetration, i.e. inches per year (ipy), mils or mm y" . Such calculations suffer from the same defects as the mdd figures in that they take into account neither changes in corrosion rates with time nor non-uniform distribution of corrosion. However, since such conversions are often made it is desirable for the initial reporter of the test results to make the calculations accurately and to report corrosion rates in both mdd and mm y or similar units. 

The characteristic mode of corrosion of some alloys may be the formation as a corrosion product of a redeposited layer of one of the alloy constituents, as in the case of the brasses that dezincify, or of a residue of one of the components, as in the case of the graphitic corrosion of cast iron. Particularly in the case of the dezincified brass, the adherent copper is not likely to be removed with the other corrosion products, and therefore the mass-loss determination will not disclose the total amount of brass that has been corroded. This is especially important because the copper layer has very little strength and ductility and the extent of weakening of the alloy will not be indicated by the mass loss. In these cases, also, the mass-loss determinations must be supplemented by, or replaced by, mechanical tests or metallographic examination, or both, to reveal the true extent of damage by corrosion. Difficulties in obtaining accurate mass losses of heavily graphitised specimens have been reported... 

The controversy that arises owing to the uncertainty of the exact values of and b and their variation with environmental conditions, partial control of the anodic reaction by transport, etc. may be avoided by substituting an empirical constant for (b + b /b b ) in equation 19.1, which is evaluated by the conventional mass-loss method. This approach has been used by Makrides who monitors the polarisation resistance continuously, and then uses a single mass-loss determination at the end of the test to obtain the constant. Once the constant has been determined it can be used throughout the tests, providing that there is no significant change in the nature of the solution that would lead to markedly different values of the Tafel constants. 

An obvious method for studying galvanic corrosion either with or without supplementary electrical measurements is to compare the extent of corrosion of coupled and uncoupled specimens exposed under identical conditions. Such measurements may use the same techniques for estimating corrosion damage, such as mass-loss determinations, as have been described in connection with ordinary corrosion tests. 

Nitric acid test t 65 wt.% HNOj Five 48 h exposures to boiling solution refreshed after period Average mass loss per unit area of five testing periods -1- 0-99 to -1- 1-20 1. Chromium-depleted areas 2. <7-phase 3. Chromium carbide... 

Acid ferric- sulphate (Streicher) test n 50wt.% H2SO4 -1-25 g/l ferric sulphate 120 h exposure to boiling solution Mass loss per unit area -1- 0-7 to -1- 0-9 1. Chromium-depleted areas 2. <7-phase in some alloys... 

Nitric-hydrofluoric acid test 1 10% HNO3 -1- 3% HF 4 h exptosure to 70° C solution Comparison of ratio of mass loss of laboratory annealed and as-received samples of same material Corrosion potential of 304 steel = -l-O-14 to -I-0-54 1. Chromium-depleted areas 2. Not for 0-phase 3. Used only for Mo-bearing steels... 

Hydrochloric acid test 1 10% HCl 24 h in boiling solution 1. Appearance of sample after bending around mandril 2. Mass loss per unit area (a) Redox pxjtential = -I-0-32 (b) Corrosion potential = -0-2 0-1 1. Alloy-depleted area 2. Not for 0-phase... 

This was described in 1959 by Streicher , and consists of one period of exposure to a boiling solution of 50 mass% H2SO4 -I- 25 g 1 Fe2(S04)j for 120 h, assessment being based on mass loss (see Table 19.4). Streicher, however, usually reports a ratio of mass loss of sample to be assessed/weight loss of annealed sample (g dm ), and as for the HNO3-HF test considers that a ratio > 1-5-2-0 indicates susceptibility for Type 304 Streicher considers a rate >0-76 mm/y to indicate susceptibility, but Brown considers a higher figure to be acceptable (see Table 19.4)... 

Assessment of cavitation-erosion is based on mass loss and the results are expressed as curves showing cumulative mass (or volume) loss V5. the time of the test. Eisenberg, have expressed the cumulative mass loss plot... 

As is the case with other types of corrosion testing, mass-loss determinations may fail to indicate the actual damage suffered by specimens that are attacked intergranularly or in such a manner as dezincification. In such cases, mechanical tests will be required as discussed already in the section on evaluation techniques. 

Test method for determining the susceptibility to intergranular corrosion of 5XXX series aluminium alloys by mass loss after exposure to nitric acid (NAMLT test) Practice for liquid sodium corrosion testing of metals and alloys... 

Austenitic stainless steels-determination of resistance to intergranular corrosion. Part 1 Corrosion test in nitric acid medium by measurement of loss of mass (Huey test) Austenitic stainless steels-determination of resistance to intergranular corrosion. Part 2 Corrosion test in a sulphuric acid/copper sulphate medium in the presence of copper turnings (Moneypenny Strauss test)... 

AU blends were semicrystalfine in nature and the mechanical properties were dominated by the PCL. The initial mass loss was very quickly in the degradation test which was thought to be associated with the rapid degradation of PEO. 

FIGURE 23.8 Mass loss versus time for liquid transmission test. 

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