Atmospheric corrosion tests recording

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... 

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

ASTM 033 2004 Standard practice for recording data from atmospheric corrosion tests of metallic-coated steel specimens... 

A conventional weather station approach has often been used to monitor atmospheric variables regsuxitng atmospheric corrosion [7]. Temperature and relative humidity may be recorded continuously, and these data are used to produce average temperatures for periods of time such as days, weeks, or months. Electrical monitoring sensors have been developed to measure when wetness exists on the surface by means of detecting a potential difference between dissimilar metals [8]. A standard device is shown in ASTM G 84, Practice for Measurement of Time of Wetness on Surfaces Exposed to Wetting Conditions as in Atmospheric Corrosion Testing. The information on time of wetness is usually reduced to a percentage or fraction of time a surface is wet in a month or in a year. 

ASTM G 33, Practice for Recording Data from Atmospheric Corrosion Tests of Metallic-Coated Steel Specimens G 50, Practice for Conducting Atmospheric Corrosion Tests on Metals G 84, Practice for Measurement of Time-of-Wetness on Surfaces Exposed to Wetting Conditions as in Atmospheric Corrosion Testing G 92, Practice for Characterization of Atmospheric Test Sites. 

There are several other aspects of atmospheric characterization which, if measured, can provide pertinent information related to the performance of materials. Probably the most important and universal is the determination of the TOW, described earlier. ASTM G 84, Practice for Measurement of Time-of-Wetness on Surfaces Exposed to Wetting Conditions as in Atmospheric Corrosion Testing, describes instrumentation and techniques for measuring TOW. This parameter can most easily (and adequately) be estimated from weather bureau records. It is generally accepted that metal atmospheric test specimens are wet when the temperature is above freezing and the relative humidity is above 80 %. There are indications that corrosion can occur under arctic conditions down to 0°F if... 

After removal at the specified exposure period, the specimens are evaluated. Visual examination of the specimens upon removal is usually performed, and a photographic record of appearance is valuable. ASTM G 33, Practice for Recording Data from Atmospheric Corrosion Tests of MetaUic-Coated Steel Specimens, can provide guidance for evaluation procedures. Before determination of mass loss, or for most other evaluation techniques, the specimens must be cleaned. Again, cleaning procedures are described in ASTM G 1 and A 380 for most materials of interest. ASTM G 1 also includes a procedure for determining when the corrosion products have been removed. After cleaning, specimens should be placed in a desiccator with fresh dessicant until ready for further evaluation. 

Considering the above, test sites should be selected to provide general corrosion performance in one or more of these atmospheric classifications. ASTM Committee G01.04 on Atmospheric Corrosion operates sites that include all three, and testing can be done in these providing the data accumulated become part of the public record. In addition, there are several private, government, and commercial testing facilities already established where exposure space can be rented. 

Various methods have been developed for measuring many of the factors that influence atmospheric corrosion. The quantity and composition of pollutants in the atmosphere, the amount collected on surfaces under a variety of conditions, and the variation of these with time have been determined. Temperature, RH, wind direction and velocity, solar radiation, and amount of rainfall are easily recorded. Not so easily determined are dwelling time of wetness (TOW), and the surface contamination by corrosive agents such as sulfur dioxide and chlorides. However, methods for these determinations have been developed and are in use at various test stations. By monitoring these factors and relating them to corrosion rates, a better understanding of atmospheric corrosion can be obtained. 

Vertical media with very high coercivities can be produced by plating into alumina pores [112], Some of these media are too hard to be easily written with present heads. Tailoring of the pore size can be used to obtain structures with the desired Hc [115, 116], however. Recording characteristics of disks have been determined [112-114, 116] such media show excellent promise as vertical recording media. In addition, structures with electrodeposited Fe in the pores were tested in life-tests at elevated temperatures and humidity and in corrosive atmospheres. They were found to perform satisfactorily. 

A feature of these mainly benign atmospheres is that the ratio of steel to zinc corrosion is less than found further west. The Soviet workers had test sites for which temperature, relative humidity, days with dew and rain, and particulate deposits were recorded over 4 years, while Table 2.21 gives information on chloride ions and sulphur dioxide (Strekalov and Berukshtis, 1965), together with corrosion rates in both open and sheltered exposures. 

The visual approach is often used in the atmospheric testing of painted, metallic-coated sheet. Extent of paint blistering, paint undercutting, and appearance of corrosion products at edges, scribes, and formed areas are typically observed and recorded. 

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