Metal Finishing Guide Book

2013

Issue link: https://metalfinishing.epubxp.com/i/218436

Contents of this Issue

Navigation

Page 550 of 843

service and more corrosive environments and also to evaluate the performance and protective properties of more durable coatings which would not be affected by the typical ASTM B117 type salt fog test. This test method is particularly applicable to the evaluation of the performance of decorative copper/nickel/ chromium or nickel/chromium coatings on steel, zinc alloys, aluminum alloys, anodized aluminum and plastics designed for severe service. This test meets the challenges of providing a simulated service evaluation to test product specifications in research and development and provide manufacturing controls for environmental changes caused by human intervention. The B368 Standard is a variation on the basic ASTM B117 Salt Spray (Fog) Test. For this variation, adjust the pH of the 5% salt solution into the range 6.0 to 7.0, and then add 0.25 grams of reagent-grade copper chloride per liter of salt solution. The test is not considered to start until the temperature within the exposure zone has reached 49°C +/- 1°C (120° +/- 2-°F) and is then run continuously for 6 to 170 hours as agreed upon between purchaser and seller prior to the start of the test. It is required that the temperature within the exposure zone be checked twice a day only on regular business days when the chamber may be periodically opened for "short" durations (preferably less than 5 min) to work with test pieces and/or replenish solution. Another variation from the standard salt spray (fog) test is in the mandatory verification for consistency of test exposure conditions. In ASTM B using "Nickel Mass Loss Coupons" rather than steel (as used in the B117 Practice, Section X3 [non-mandatory]). The B368 Fig. 5. Typical cyclic-type corrosion test chamber Standard uses corrosion test with PLC control for automatic operation of chamber apparatus that meets changeable atmospheres, temperatures, and the requirements for the ASTM durations of various steps in cycle. B117 Standard and will withstand the increased temperature and stronger electrolyte solution used for this test. ASTM G85— Standard Practice for Modified Salt Spray (Fog) Testing Five variations of this standard have been developed to accommodate its use to different purposes. The variation that is used by interested parties in any situation must be agreed upon prior to the start of testing. Following are brief explanations of each of the five individual test variations: Annex 1—Acetic-Salt Spray (Fog) Testing The Acetic Acid-Salt Spray (Fog) Test is used to test ferrous and nonferrous metals and inorganic and organic coatings for resistance to additional and more corrosive environments than the ASTM B117 Standard. This test is designed as a continuous exposure test without interruptions. It uses a 5 ±1 part by mass 541

Articles in this issue

view archives of Metal Finishing Guide Book - 2013