Salt spray testing method

The validation results require changes in the salt spray test method description and maybe in the performance. 

Environmental Engineering Considerations Laboratory Tests Methods of Salt Spray Testing Methods of Compound Corrosion Test Cosmetic Corrosion Lab Test... 

Sa.lt Spray Tests. One of the older accelerated corrosion tests is the salt spray test (40). Several modifications of this imperfect test have been proposed, some of which are even specified for particular appHcations. The neutral salt spray test persists, however, especially for coatings that are anodic to the substrate and for coatings that are dissolved or attacked by neutral salt fog. For cathodic coatings, such as nickel on steel, the test becomes a porosity test, because nickel is not attacked by neutral salt fog. Production specifications that call for 1000 hours salt spray resistance are not practical for quahty acceptance tests. In these cases, the neutral salt spray does not qualify as an accelerated test, and faster results from different test methods should be sought. 

The solution was applied to the surface of cold-rolled steel, dip-galvanized steel sheet, and aluminum strip for degreasing and passivating in a single operation at 40°C for 90 s. The surfaces were then lacquered (85-100 pm thickness) and tested in a salt-spray test for 480 h without showing subsurface migration and blistering. The method is especially useful in the automobile industry for coated sheet [191]. 

Simplicity and reliability of operation make AC impedance measurements attractive as a technique in the evaluation of coating integrity. As opposed to classical salt spray test, analysis times are shorter with the AC impedance technique and quantitative data are obtained permitting relevant mechanistic Information to be derived. Impedance test methods are likely to find many applications in the resolution of unsolved practical problems ( .) ... 

E-coat stripping. Both plasma-treated panels show excellent corrosion protection performance as compared to the control panels. All [2A] panels with different plasma treatments and plasma polymer coatings, which were corrosion tested in both SO2 and Prohesion salt spray tests, were similarly scanned, and the corrosion width was evaluated by using a scanned image and computer calculation of the corroded area. Figure 31.19 compares the corrosion width obtained by the two methods. 

Figures 31.23 and 31.24 show typical scanned images of SO2 and Prohesion salt spray-tested [7B] panels, respectively. Visual observation of these images reveals that the plasma-modified panels of [7B] have outperformed both control panels in the SO2 salt spray test. These plasma film combinations were prepared on deoxidized [7B] surfaces without any plasma cleaning pretreatment. Figure 31.23 also shows an image of a panel that had simply been deoxidized prior to the application of E-coat, which performed excellently in the SO2 salt spray test. Figure 31.25 compares the corrosion width obtained by the two methods. The comparisons shown in Figures 31.19, 31.22, and 31.25 indicates that the results obtained by the two methods do not match, partly due to the different duration of tests, and that samples which show good results in one test do not do as well in the other test.

Evaluation of cabinet corrosivity. In order to determine the corrosivity of the corrosion cabinet environment eight tests were performed [5] according to the standard method of the neutral salt spray test (Table 1). The results of corrosion rate of RS and the main statistical parameters such as the number of reference samples n, average RS mass m and RS mass loss Am of each RS, average RS surface area S and surface area of each RS Sn, mean averages of all eight experiments and their standard deviations are presented in Table 2a and 2b. 

Uncertainty of mass loss measurement. The standard method of the neutral salt spray test does not indicate the mass of RS. Mass loss was found as a difference between the RS prepared for the corrosion test and the RS after the corrosion test and corrosion product stripping as well as protective coating removal from the RS (Table 1). Such a mass loss determination is based on three components (1) mass loss determination by weighing (accuracy 0.5 mg and standard deviation 0.3 mg) before the neutral salt spray test and after it, (2) determination of difference and (3) cor-... 

Additional specifications from other corrosion test standards [2, 3] are required for the standard method of the accelerated corrosion test in the neutral salt spray test cabinet at 35 2 °C within 96 h. For the evaluation of corrosion data quality, the test should be performed according to the requirements of contemporary standards such as ISO/IEC 17025 [9] and, therefore, the corrosion test data uncertainty must be determined. 

Corrosive media that cause a particularly strong attack and thus damage in the bonded joint within relatively short time. The best-known test method is the salt spray test. 

The specimen (after these tests) is evaluated for its extent of corrosion. If it would be genuine research, we could use various electron microscopies such as TEM, SEM, XPS, etc. However, we usually use a rating number method for the evaluation from the practical standpoint. Figure 10 shows schematic figures for the method. We can evaluate the distribution situation by the naked eye, by comparing the tested specimen to the standard samples. There are some other methods similar to the salt spraying test and the CASS test. However, the basic concept for the evaluation method is almost the same. The solution, temperature, and amount of spraying are varied from test to test. 

Japanese Industrial Standard (JIS) 2371 (2000) Method of salt spray testing... 

In these tests, Zn/Ni and Zn/Co show better corrosion protection than zinc (thickness for thickness), but the salt spray test is not very reliable for comparison of corrosion protection. The authors indeed indicate the need for methods yielding a better correlation with atmospheric corrosion. Thinner chromate layers result in poor corrosion protection. 

In a salt spray test the sample is brought in contact with a saline fog in a closed chamber for a certain number of hours. The fog is formed by atomizing a NaCl solution by means of a nozzle. The high corrosivity of the artificial fog simulates that of a marine atmosphere, but the method does not offer a realistic model of more general atmospheric corrosion conditions, because it involves neither the presence of SO2 nor humidity cycling. In order to accelerate the corrosion, acetic acid or copper chloride is sometimes added to the saline solution. 

The strength of bonded PP joints can be measured in accordance with the well-known testing standards such as, for example, DIN 53281, 53282, 53383 or 53289. In some cases, the thickness of the adherends should be different from that used on normal metal parts because the strength of PP is lower. For example, in the case of shear tests with single overlapped joints, the thickness of the PP parts should be 4 mm or more. Also the aging conditions can be in accordance with standards such as DIN 53286 or ASDM B117 (salt spray test). T) ical test methods for bonded... 

Corrosion in Artificial Atmospheres Cosmetic Corrosion Test Metiiod for Automotive Parts Methods of Neutral Salt Spray Testing Salt Spray Test... 

Whether due to the lack of an alternative test method or other reasons, the salt spray test has endured in spite of clear data that, in some cases, it is misapplied and misused, thereby providing erroneous information. As indicated in paragraph 3.2, Prediction of performance in natural environments has seldom been correlated with salt spray results when used as stand alone data. Significance and Use, a modification made to ASTM B 117 in 1985, paragraph X2.2 specifically states, It should be noted that there is usually not a direct relation between salt (fog) resistance and resistance to corrosion in other media because the chemistry of the reactions, including the formation of films and their protective value, frequently varies greatly with the precise conditions encountered. ... 

Immersion Tests—Continuous total immersion tests were developed more recently to provide simpler, rapid, and more reproducible test methods than the salt spray tests. Although plain sodium chloride solutions do not cause exfoliation during the desirable short periods of immersion, formulations of chloride-nitrate solutions were found that produced severe exfoliation of highly susceptible alloys of various types in only one to four days. Optimum test conditions differed for separate alloy families [J]. 

Specimens may be of ciny practical size or shape. However, it is advisable not to use too small a specimen since visual examination is the key evaluation method. It is recommended that flat specimens at least 50 mm by 75 mm in size and full section thickness be used with the specimen length oriented in the direction of principal deformation of the mill product. Larger sized panel specimens are desirable for salt spray testing or outdoor exposures. 

The current salt spray test, in which the plated specimen is exposed to a spray or fog of sodium chloride solution, is the most widely used accelerated corrosion test for coatings, and various procedures have acceptance tests in standard specifications in numerous countries. Over the years, the procedure has employed sodium chloride solutions of concentrations between 3 and 20 %, sometimes with the addition of hydrochloric acid or hydrogen peroxide. The salt spray test [ASTM B 117, Test Method of Salt Spray (Fog) Testing] has largely fallen into disrepute because of the recognition that its reproducibility and correlation with outdoor exj>osure were often poor. Cyclic salt spray testing as well as alternate electrolytes such as the "prohesion test solution have been found to produce more realistic results. 

The addition of acetic acid to the salt solution used in the salt spray tests was introduced first in 1945 and is currently Annex A1 of ASTM G 85 [Practice for Modified Salt Spray (Fog) Testing]. The acidified test is much more corrosive than the normal salt spray test and is capable of producing a pattern of attack similar to that developed in outdoor service for decorative chromium plate on steel or zinc. It is much slower than the copper-accelerated acetic acid-salt spray (CASS) test in ASTM B 368 [Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)], [77] which resembles it in effect. 

This test has the advantage over the salt spray test in that it excludes the effect of specimen shape and suspension method. In addition, it is possible to directly determine and control the droplet size. Moreover, effects due to the size and shape of the test chamber are excluded. 

Applicable test methods include [28] Continuous Salt Spray Tests (ASTM B 117), Neutral Salt Spray Test (ASTM B 117), Acetic Acid Salt Spray Test, Copper-Accelerated Salt Spray Test (CASS) (ASTM B 368), Cyclic Salt Spray Tests, the Copper Development Association (CDA) Test, the Hitachi Salt Spray Test, Climate Tests, The Humidity Test, The International Electrotechnical Commission/Intemational Organization for Standardization (lEC/ISO) Test and Mud Test. 

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