Metal Finishing Guide Book


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ASTM B117 — Standard Practice for Operating Salt Spray (Fog) Apparatus The ASTM B117 Standard is primarily used to test the corrosion resistance of organic and inorganic coatings on metals. Examples are paint or plated finishes on metal items and exposure of products to "marine" or "near-shore" environments. This standard will also be the base against which this article will describe other corrosion tests. The B117 Standard is a "static" (constant) condition, continuous test, preferably run in multiples of 24-hour periods. The test pieces are exposed to a salt Fig. 2. Typical water-jacketed-type corrosion test chamber fog atmosphere from atomized mostly used for static condition tests. solution made up of 5% sodium chloride and 95% ASTM D1193 Type IV water by mass and held to purity standards specifying that it contain: not more than 0.3% by mass total impurities. Halides (Bromide, Fluoride, and Iodide) other than Chloride, shall constitute less than 0.1% by mass of the salt content. Copper content shall be less than 0.3ppm by mass. Sodium Chloride that has had anti-caking agents added shall not be used because such agents may act as corrosion inhibitors. This solution is then atomized into the chamber exposure zone, which is maintained at a temperature of 35 +/- 2°C (95 +/ - 3°F) and a relative humidity of at least 95%, creating a fog that has a condensate collection rate of 1.0 to2.0 ml/hr per 80 m2 of horizontal collection area. To maintain these conditions, the chamber is heated and best maintained with a wet bottom condition in the exposure zone. The equipment needed to maintain these test conditions will meet the requirements described in Table II and be made such that all component parts that come in contact with the exposure zone, water, or solutions are made of, or coated with, inert materials. Typical test chamber compoFig. 3. Typical large-size drive-in-type nents and operational conneccorrosion test chamber. tions are illustrated in Fig.1. ASTM D1735 — Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus The ASTM D1735 Standard uses a standard fog-generating chamber as used for the ASTM B117 Standard. The primary variations are the chamber temperature, 539

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