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Phosphating of tool steel
We use a casting of CH13 (hot worked tool steel investment casting)for our component making. This casting undergoes heat treatment (spherodising, machining, gas carburising, hardening and tempering, Hardness = 60 HRC) followed by sand blasting for surface cleaning.
While performing manganese phosphating, we find white patches. We are looking for a uniform black colour. Can someone help to avoid white patches. Phosphating is followed by tectyl 272 oiling. Corrosion test (as per ASTM ASTM B117 [affil. link to spec at Techstreet] ) on the component with white patches show a good corrosion resistance.G R Patel
Manufacturer, Power Equipments - Vadodara, Gujarat, India
April 9, 2012
Q. Dear sir
We are also facing the white patches after manganese phosphating. Can any one suggest the same for better control?