Problem Solving Guide for Black Oxide

 

PROBLEM INVESTIGATE
Non-Uniform or Spotty Coatings Cleaning/Surface Prep (oxides, scale, buffing or drawing compounds)
Scum on the Surface of the Black Oxide Bath
Parts Nesting Together
Selective Heat Treatment
Inadequate Control of Black Oxide Temperature
Light Gray Coatings Bath Temperature Too Low
Heat Treatment (nitrided or carbonitrided steel)
Blackening Time Too Short
Inadequate Surface Activation
Red/Mahogany Coatings High Silicon Content in the Base Metal
Parts Were Previously Phoshate Coated
Non-Ferrous Metal Contamination in the Black Oxide Bath
Brown Rub-Off Bath Temperature Too High
Slow Transfer Time to the Rinse After Black Oxide
High Concentration of Colloidal Iron in the Black Oxide Bath
Unremoved Stamping or Forming Lubricant
White Residue Poor Rinsing After the Black Oxide Bath
Carbonate Bleed Out – Powdered Metal Components, Blind Holes or Assemblies

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