ASTM B578-87 pdf free.Standard Test Method for Microhardness of Electroplated Coatings.
This test method covers the determination of the hardness of metallic coatings upon various substrates. The mea-surements are made with the Knoop indenter under a test loadof 0.245 N (25 gf) or 0.981 N (100 gf).
This standard does not purport to address all of thesafety concerns，if any, associated with its use. lt is theresponsibility of the user of this standard to establish appropriate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
No single test load is applicable to all coatings.Use aload of 0.245 N for soft coatings (from 50 to 300 HK) and aload of 0.981 N for hard coatings (greater than 300 HK).3.2.1 A load of less than 0.245 N is not recommended.However，when the length of the diagonal is great enough at aload of 0.245 N, which may occur for very soft coatings suchas tin and indium, a lighter load or a lower magnification shallbe specified provided the requirements of 3.3 are met. Whentesting extremely hard coatings, a load greater than 0.981Nmay be used provided this is specified in the purchase order.The Knoop hardness number decreases appreciably with loadsfrom 0.245 N to 0.981 N especially for the higher hardnessnumbers.
Measure the length of the long diagonal to within 0.25um or 0.4 %, whichever is larger, at the magnification specifiedin Test Method E 384.
When readings are taken in a direction parallel to thesubstrate, space them from each other by at least the length ofthe long diagonal. When two readings are taken in the directionof the short axis，separate them by at least the length of thediagonal perpendicular to the substrate (short diagonal). Insuch cases, the distance from the substrate and from the outersurface of the coating to an edge of the indentation shall be atleast the width of the short diagonal.
If the electroplated coating is cracked，or if cracks or“butterfly”‘markings (Test Method E 384,7.2) appear when theindentation load is applied or removed, the hardness measure-ment is invalid.ASTM B578 pdf download.