Corrosion testing standardized methods

There is no standard or preferred way to cany out a corrosion test the method must be chosen to suit the purpose of the test. The principal types of tests are, in decreasing order of rehability ... 

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. 

ASTM G 16, Guide for Applying Statistics to Analysis of Corrosion Data—Statistical analysis methods are presented. The methods discussed in this standard allow investigators to determine the significance of their results with the inherent variation observed in corrosion testing. This method includes error analysis, variability measures, standard statistical tests, curve fitting methods, and sample calculations. 

Factors may throw off these rates—these are outlined in ASTM G3I, Standard Practice for Laboratory Immersion Corrosion Testing of Metals. Coupon-type tests cannot be correlated with changing plant conditions that may dramaticahy affect process equipment lifetimes. Other methods must be used if more frequent measurements are desired or correlation with plant conditions are necessary. 

Standard method for evaluation of painted or coated specimens subjected to corrosive environments Standard test method of salt spray (FOG) testing... 

British Standard Method for Determination of Resistance to Intergranular Corrosion of A ustenltic Stainless Steels Copper sulphate-Sulphuric acid Method (Moneypenny Strauss Test) BS 5903 (1980)... 

A detailed and well-referenced account of electrochemical methods of testing has been written by Dean, France and Ketcham in a section of the book by Ailor. ASTM G5 1987 outlines standard methods for making potentiostatic and potentiodynamic anodic polarisation measurements and ASTM G3 1974 (R1981) gives conventions applicable to electrochemical measurements in corrosion testing. 

A convenient size for a circular coupon is 3 8 cm dia., a thickness of 0 - 32 cm and a central hole of 1 1 cm. Although inherent in the philosophy of corrosion testing, the use of coupons with surfaces that simulate those in service has been found to be unsatisfactory owing to irreproducibility, and the standard procedure normally adopted is to abrade down to 120-grit. ASTM Method G4 1984 gives details of preparation of specimens, evaluation of replicate exposures and the application of statistical methods. 

A number of standards exist for the determination of some of these parameters. BS 1377 Part 3 1990 refers to methods of tests for soils for civil engineering purposes, and Part 9 refers to these and corrosivity tests in situ. It is significant that the standard draws attention to the fact that the results of the tests that are described should be interpreted by a specialist. ASTM tests for pH and resistivity of soil used for corrosion testing are covered by G51 1977(R1984) and G57 1978 (R1984), respectively. 

ASTM G4 (latest revision) gives guidance for conducting plant corrosion tests, and in particular, for various methods for mounting specimens (coupons) in process plant. This standard evolved from ASTM and NACE Technical Committees. 

Corrosive sulfnr componnds can be detected by their effect on copper and the form in which the general copper strip corrosion test (ASTM D1838) for petrolenm prodncts is applied to liqnefied petrolenm gas. Hydrogen sulfide can be detected by its action on moist lead acetate paper, and a procedure is also used as a measure of sulfur compounds. The method follows the principle of the standard Doctor test. 

Panels of high strength aluminum alloy (7075-T6) were used in this study. The panels were approximately 10 x 3 x 0.032 inch (25 x 7.5 x 0.08 cm) in size. The test environments for coating evaluation were (1) a 5% NaCl spray (fog) chamber according to ASTM Standard Method of Salt Spray (Fog) Testing (B117-73), and (2) a modified 5% NaCl/S02 spray (fog) chamber with SO gas introduced periodically - ASTM Standard Practice for Modified Salt Spray (Fog) Testing (G85-84(A4)). In the latter case, a constant spray of 5% NaCl was maintained in the chamber and SO2 was introduced for one hour four tines a day (every 6 hours)( ). Coated test panels were examined for corrosion after one- and two- eek exposure periods. 

Laboratory Corrosion Test. The laboratory test procedure for the determination of corrosion rates of coal slurry used in this study was adapted from the method developed by Bomberger (26). The corrosion rates were determined by using ASTM Standard Corrosion Test, also known as the Total Immersion Method (27). The Bomberger technique consists of keeping coal slurry in suspension in a two-liter reaction vessel at a constant temperature. The corrosion rates are determined either by actual weight loss of steel coupons... 

The standard method for the test cabinet corrosivity determination is described in ISO 92271 [1] but we failed to find any information about the validation of this method or its metrological parameter evaluation. On the other hand, it is necessary to determine from the experimental point of view whether this technique is reliable enough as a standard method. A procedure is described in ISO... 

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-... 

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