Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 297 of 331

TYPES OF TESTS For the purposes of this discus- sion ASTM B 117 is described first. The other ASTM Corrosion Test Standards discussed are de- scribed in terms of how they vary from the basic B 117 Standard. Only those parts of these stan- dards, which are different from the B 117 standard, will be dis- cussed. ASTM B 117—Operating Salt Spray (Fog) Apparatus Fig. 2. Typical water-jacketed-type corrosion test chamber mostly used for static condition tests. The ASTM B 117 Standard is pri- marily used to test the corrosion resistance of organic and inor- ganic coatings on metals. Exam- ples are paint or plated finishes on metal items and exposure of products to marine environ- ments. This standard will also be the base against which this article will describe other corrosion tests. The B 117 Standard is a static (constant) condition, continuous test, prefer- ably run in multiples of 24-hour periods. The test pieces are exposed to a salt fog atmosphere from atomized solution made up of 5% sodium chloride and 95% ASTM D 1193 Type IV water by mass and held to purity standards specifying that it contain less than 0.1% sodium iodide, 0.3% total impurities, and less than 200 ppm total solids.This solution is atomized into a chamber, which is maintained at a temperature of 35 + 1.1 or - 1.7°C (95 + 2 or - 3°F) and a relative humidity of at least 95%. 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 de- scribed in Table II and be made such that all component parts that come in contact with the exposure zone, water, or solu- tions are made of, or coated with, inert materials. Typical test chamber compo- nents and operational connec- tions are illustrated in Fig.1. Fig. 3. Typical large-size drive-in-type corrosion test chamber. ASTM D 1735—Testing Water Resistance of Coatings Using Water Fog Apparatus The ASTM D 1735 Standard uses a standard fog-generating chamber as used for the ASTM B 117 Standard. The primary variations are the chamber tem- 296

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