Atmospheric corrosion testing

H. Guttman, Atmospheric and weather factors in corrosion testing. Atmospheric Corrosion (W. H. Ailor, ed.), Wiley, New York, 1982, p. 51. 

Carbonyl sulfide reacts with chlorine forming phosgene (qv) and sulfur dichloride [10545-99-0] and with ammonia forming urea and ammonium sulfide [12135-76-1]. Carbonyl sulfide attacks metals, eg, copper, ia the presence of moisture and is thought to be iavolved ia atmospheric sulfur corrosion (27,28). Its presence ia propane gas at levels above a few ppm may cause the gas to fail the copper-corrosion test. 

Corrosion test methods, useful for comparison purposes, usually have no correlation to actual corrosion resistance in atmospheric exposure. 

The above work is important, since many practical corrosion systems involve a thick but porous film of corrosion products, e.g. rusting, sul-phatising, tuberculation and atmospheric corrosion, and the approach may lead to a more valid corrosion testing technique for these situations. 

Table 4.11 Atmospheric corrosion tests on copper and copper alloys...

Exposure of the samples to a controlled moist atmosphere containing sulphur dioxide, as recommended in BS 1615 1972, Method H, is an example of a test bridging the gap between sealing tests and accelerated corrosion tests. After exposure for 24 h at 25 2°C, poorly sealed films show a persistent heavy white bloom, while good sealing produces at the most a slight superficial bloom. 

Tests carried out for particular purposes may make use of other special means to measure the progress of corrosion. For example, changes in the reflectivity of polished surfaces have been used as a sensitive means of following changes in the very early stages of corrosion in laboratory studies. A similar technique has been applied on a practical scale in connection with the direct evaluation of the relative merits of different alloys as used for mirrors in searchlights exposed to corrosive natural atmospheres. 

Legault, Mori and Leckie have used open-circuit potential vs. time measurements and cathodic reduction of rust patinas for the rapid laboratory evaluation of the performance of low-alloy weathering steels. The steel specimens are first exposed for 48 h to the vapour of an 0-(X)l mol dm sodium bisulphite solution maintained at 54°C (humid SOj-containing atmosphere) to stimulate corrosion under atmospheric conditions. They are then subjected to two types of test (tt) open-circuit potential-time tests for periods up to 3 000 s in either distilled water or 0 -1 mol dm Na2S04 and... 

Practice for making and using U-bend stress corrosion test specimens Recommended practice for laboratory immersion corrosion testing of metals Method for vibratory cavitation erosion test Practice for recording data from atmospheric corrosion tests of metallic-coated steel specimens... 

Recommended practice for conducting atmospheric stress corrosion tests on metals Test method for pH of soil for use in corrosion testing... 

Corrosion tests in artificial atmosphere general requirements... 

Metals and alloys removal of corrosion products from corrosion test specimens Metals and alloys atmospheric corrosion testing general requirements for held tests Corrosion of metals and alloys. Classification of corrosivity of atmospheres Corrosion of metals and alloys. Guiding values for the corrosivity categories of atmospheres... 

Corrosion tests in artificial atmospheres salt spray tests... 

Test /. -corrosion tests in artificial atmosphere at very low concentrations of polluting gases... 

Atmospheric corrosion is the most extended type of corrosion in the World. Over the years, several papers have been published in this subject however, most of the research has been made in non-tropical countries and under outdoor conditions. Results of outdoor and indoor corrosion rate and corrosion aggressivity in tropical corrosion test stations of Cuba and Mexico are reported. 

Resistance to Water in Snlfnr-Dioxide-Containing Atmospheres. For standards, see Table 1 ( Corrosion testing S02 and S02 resistance ). General conditions are standardized for exposing samples to a varying climate where water condenses in the presence of sulfur dioxide, so that tests in different laboratories give comparable results. The test allows rapid detection of defects in corrosion-inhibiting systems. 

The impetus for further developments was the recognition of the economic significance of corrosion phenomenon during the 19th century that led the British Association for the Advancement of Science to sponsor corrosion testing projects such as the corrosion of cast and wrought iron in river and seawater atmospheres in 1837. Early academic interest in corrosion phenomenon (up to the First World War) was followed by industrial interest due to the occurrence of equipment failures. An example of this is the corrosion-related failure of condenser tubes as reported by the Institute of Metals and the British Non-ferrous Metals Research Association in 1911. This initiative led to the development of new corrosion-resistant alloys, and the corrosion related failure of condenser tubes in the Second World War was an insignificant problem. 

Two weeks to a month is recommended for plant tests. Atmospheric corrosion and soil corrosion involving low-corrosion rates require periods of the order of several years of exposure. 

All the atmospheric corrosion tests discussed thus far should be used as guides, and suitable tests should be devised and conducted in the environment of interest to assess the corrosivity of the environment. 

Some useful and pertinent information on atmospheric corrosion test site plans, hardware and other relevant information in the literature25 30 may be used in planning atmospheric corrosion testing program. 

Galvanic corrosion testing under atmospheric exposures has been standardized and bears the titles ISO 7441-84, ASTMG 104-89 for plate tests and ASTM G116-93 for wire-on-bolt tests.21,34,35 A form of test assembly for galvanic corrosion testing is shown in Figure 2.5. 

ASTM G84, Standard Practice for Measurement of Time-of-Wetness on Surfaces Exposed to Wetting Conditions as in Atmospheric Corrosion Testing, West Conshohoken, PA, 1993. 

H.H. Lawson, Atmosphere Corrosion Test Methods, NACE International, Houston, TX, 1995. 

ASTM G33, Standard Practice for Recording Data from Atmospheric Corrosion Tests of Metallic-coated Steel Specimens, West Conshohoken, PA, 1988. 

The long-term atmospheric corrosion tests conducted in Australia, Brazil, Canada, Czechoslovakia, Finland, Germany, Japan, Latin America, New Zealand, Norway, Russia, Scandinavia, Singapore, Spain, Sweden, Taiwan, UK and USA along with the number of... 

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