ASTM B489-85(2013) pdf free download.Standard Practice for Bend Test for Ductility of Electrodeposited and Autocatalytically Deposited Metal Coatings on Metals.
ASTM B489-85(2013) covers a test procedure for determining the ductility of electrodeposited and autocatalytically deposited coatings on sheet or strip basis metals. The purpose of the test is to determine the resistance of metal coatings to cracking during distortion.
Test Methods E8 can be used if the coatings are too ductile and require mandrels too small to be practical.
6. Test Specimen
6.1 Flat specimens. 10 mm wide, and not less than 150 mm long, shall be cut from the electroplated or coated article if the shape permits. no closer than 25 mm from the edges. Guillotine shears are preferred. but any convenient method may be used. Basis metal thickness and temper shall be suitable to permit bending around the smallest diameter mandrel, if necessary. Low-carbon AlSl 1010 to 1025 steel strip or sheet. 0.25 to 1.0 mm thick is usually suitable. Basis metals that have low ductility can initiate cracks that can propagate through the coatings. The procedure indicated in 6.2 shall then be followed.
6.2 When the shape is such that a test specimen cannot be obtained from the part, a test panel may be prepared of appropriate basis metal, such as low-carbon steel (see 6. 1), with the same coating system in the same baths. The panel shall be sufficiently large to obtain several pieces after trimming 25 mm from the edges. The specimens shall he prepared in accordance with 6.1. Brass or copper panels may he used instead of copper-electroplated zinc alloy panels.
6.3 The long edges of the test pieces shall he rounded or chamfered by tiling or grinding.
7. Procedure
7.1 Place the largest mandrel in the vise. Bend the test specimen, with the coaling outward, over the mandrel so that as the bend progresses the test specimen will remain in contact with the top of the mandrel. Continue bending with slow, steadily applied pressure until the two legs are parallel. If there are no cracks visible under a lOx magnifier, repeat the test, using new specimens, on progressively smaller-diameter mandrels. until cracks appear across or through the coating. Take the preceding mandrel diameter as the value for the ductility determination. If the coating is electrodeposited chromium, the specimens may require heating or aging to overcome temporary hydrogen embrittlement. A procedure to overcome hydrogen embrittlement is covered in Guide B 177.
7.1.1 Small cracks not greater than 1.5 mm long, confined to the edges of the test specimen do not signify failure.
7.1.2 At times, no single crack may develop over the convex surface. If jagged cracks, or a series of shorter cracks develop (excluding edges), they signify failure.