17-July-2006
Technical Bulletin 002

8339/8340 Enclosure Surface Corrosion

Overview

This technical bulletin describes a non-detrimental surface corrosion on the 8339/8340 stainless steel enclosure that may occur during long term exposure to certain types of environmental conditions.

Background

Research conducted by AWI and Hoffman Inc. found that 304 stainless steel exposed to atmospheres with chlorine or chloride compounds with concentrations above 100-200 ppm may experience a surface corrosion showing up as a streaked, non-uniform brown color. This is especially true in chlorine-rich environments such as locations near sea water. High humidity, high ambient temperatures, long term exposure, locations near the sea coast, and areas of higher chlorine/chloride concentrations, all exacerbate the potential for surface corrosion.

Interestingly, type 304 stainless steels pass the 100 hour, 5% neutral salt spray test (ASTM B117) with no rusting or staining of the samples. However, it has been observed in the field that long term exposure to salt mists from the ocean, type 304 stainless steels are prone to pitting and crevice corrosion accompanied by severe discoloration.

Under the above mentioned environmental conditions, surface corrosion and surface discoloration may occur after long term exposure. There is no long term detrimental affects on the enclosure or the sensor. If required, surface cleaning can be performed with a mild abrasive stainless steel cookware cleaner. Once cleaned, a coat of a quality automotive wax may help preserve the appearance. If cleaning or waxing is performed, care should be taken not to abrasively clean or wax the windows on the top of the 8339/8340 enclosure. If located in an area where high chlorine concentrations are anticipated, or if the discoloration is not acceptable, polyurethane painting or a nonmetallic enclosure may be the solution.

Conclusions

Although not aesthetically pleasing, the surface corrosion is not detrimental to the function over the life of the enclosure or the sensor. Painting or periodic cleaning can be done if required.

www.allweatherinc.com

For specifics on any instrument, call 1-800-824-5873,
email us at marketing@allweatherinc.com
or fill out a request for more information form