Corrosion test results

These considerations will significantly affect the location of test specimens in field testing. It is clearly important to ensure that the conditions of exposure are accurately known so that the corrosion test results may be interpreted with respect to the end-use requirements. 

Table 1 - Corrosion test results of coated 7075-T6 A1 alloy exposed to salt/S02 fog environment.

Corrosion Test Results The corrosion rates were determined using a 10 wt% to 40 wt% coal water slurry with 147 to 417 /m coal particles. The corrosion rates ranged from 1.223 X 10 IPY for Illinois //6 to 1.272 X 1(T2 IPY for Indiana 3 coal slurry consisting of 40 wt% each coal. 

Corrosion Test Results in a Vapor Medium of HI-lj-HjO (1/1/6) Vapor at Various Temperatures for 1,000 h Duration... 

Although the panel with the plasma deposited film followed by priming with E-coat is visually better, the use of the corrosion width provides a method for quantifying the improvement in the corrosion performance. Also the factor of about 2 difference in corrosion width between the two chromate conversion-coated panels is difficult to obtain from the qualitative difference observed from the scanned images. It can be seen from this comparison of three panels that the use of the measured corrosion width makes the differentiation of corrosion performance much easier. This method of evaluating corrosion test results is used to determine if the combination of the two bests could indeed yield the better corrosion protection of aluminum alloys. 

Figures 28.3 and 28.4 depict corrosion tests results obtained for 2024-T3 and 7075-T-6 respectively. The first picture (from left), CC Deft, represents the control sample prepared by chromate conversion coating and chromated spray primer (Deft). The second sample, CC E-coat, is prepared by the same procedure for the CC Deft except that E-coat replaced Deft primer. The third sample is prepared by applying the same E-coat directly (without chromate conversion coating) on the...

Figure 28.23 shows the typical pictures of Prohesion tested sheets with different scribes and depths. From the visual examination of the tested panels, a general conclusion can be made that the U-type scribe resulted in much more corrosion through the corrosion test, but the scribe depth had very little effect on the corrosion test results. 

Figure 31.29 summarizes the corrosion widths along the scribed lines that were calculated from (1) SO2 salt spray-tested and (2) Prohesion salt spray-tested A1 alloy panels and their corresponding control panels. As seen from Fig. 31.29, the corrosion test results showed that the plasma coating systems based on the chromate-free spray primers provided excellent corrosion protection for the A1 alloys studied. 

The corrosion widths of Prohesion salt spray-tested IVD Al-coated Al panels were calculated and are summarized in Figure 32.6. As is evident from the data, after 12 weeks of Prohesion salt spray testing, IVD/plasma polymer/spray paint systems showed better corrosion protection overall than IVD/plasma polymer/E-coat systems. All the IVD/plasma polymer/spray paint systems outperformed the cathodic E-coated controls and showed corrosion test results comparable to those of the Deft primer oated controls. 

CORROSION TEST RESULTS (COLD-ROLLED STEEL)... 

Effect of Oxides at the Interface on Corrosion Test Results... 

The effect of interface of steel on the corrosion test result is summarized in Table 33.2. The results found for the panels, which were E-coated without phosphate or plasma polymer coatings, are quite astonishing. A scribe creep of 3.0 mm in a 4-week corrosion test was obtained for an oxide-removed CRS surface (without zinc phosphate nor plasma polymer), which is better than the E-coat on the... 

Table 33.2 Effect of the Presence or Absence of Oxides on the Corrosion Test Result Scribe Creep Width on GM Scab Test...

Figure 33.7 depicts the influence of plasma pretreatment of CRS surface as well as the hydrophilicity of the plasma polymers on corrosion test results. The left half of the bar graph represents hydrophilic interface and some of top surface are also hydrophilic. The right half of the bar graph represents the water-insensitive interface and nonhydrophilic top surfaces except the plasma polymer of CH4, which was intentionally kept in air for 10 min before application of E-coat. The figure indicates two important factors, i.e., the removal of oxides from CRS/plasma polymer interface, and nonhydrophilic top surface of plasma coatings, for corrosion protection of CRS by plasma interface engineering, which involves application of cathodic E-coat. While the air exposure of plasma polymer of CH4 severely deteriorated the corrosion protection of E-coated sample, the same exposure of TMS surface showed no effect. This difference seems to reflect the reactivity of double bonds described in Chapter 7. 

Table 33.3 Effect of Removal of Lead from E-coat on the Corrosion Test Result...

Abstract Quality control of corrosion test results implies the validation of the corrosion test method and estimation of the uncertainty of corrosion rate measurement. The corrosion test in an artificial atmosphere of the salt spray mist needs evaluation of corrosivity of the test cabinet by reference specimens. Such calibration of corrosion environment raises very strict requirements for the method description and details of all procedures and used specimens. Reliable corrosion measurements by spray tests require validation of the experimental device together with the experimental procedure and determination of corrosivity uncertainty of the test cabinet environment. 

ISO 9227 [1] does not specify in detail many necessary parameters and does not determine the precision of such a test method. The precision and accuracy of corrosion determination are influenced by many factors preparation of specimens, conditioning, removal of corrosion products, cleaning, drying, etc. In literature on the corrosion tests we failed to find any information concerning the quality of corrosion tests results. The aim of this paper is to call attention to the problems in the corrosion measurement data quality and the necessity to evaluate the uncertainty for measurement results. We attempted to show the main components of uncertainty of the result in such a measurement on the basis of the experimental evaluation of the corrosivity of the spray test corrosion cabinet by means of reference specimens. 

Electrochemical and Electrical Methods. Electrochemical and electrical methods for studying film properties and corrosion phenomena have been extensively reviewed (29-31). Comparisons of corrosion test results with direct current measurements of conductivity suggest that visible corrosion is associated with film resistance less than about 1 Mohm/cm, but this condition may well correspond with the occurrence of virtual pores in the film allowing development of local conductive pathways. In studies of the equivalent alternating current resistance as a function of frequency, Kendig and Leidheiser (44) found that the development of a region of slope -1 on a log permittivity versus log frequency plot... 

B. Wessling and J. Posdorfer. Corrosion prevention with an organic metal fPolyanilin) corrosion test results. Electrochimica Acta, 1999, Vol. 44, pp. 2139-2147. 

J.H. Prayer, W.E. Berry, W.K. Boyd, Evaluation of slow strain-rate stress corrosion tests results, in J.B. Wheeler, H.M. Hoersch, E.J. McGhnchey, H.P. Mahy (Eds.), Stress Corrosion... 

Wessling, B, Posdorfer, J. 1999. Corrosion Prevention with an Organic Metal (PolyanUine) Corrosion Test Results. Electrochim. Acta, 44, 2139. 

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