Black Spots After Copper Coating: Helpful Cause Check

Summary for black spots after copper coating Discussion

Black spots after copper coating are the issue raised by Jay Sona of Metlab, who asked how to correct discoloration on carburising-treated low carbon parts. In response, the answerer notes that "cyanide bleedout" is frequently a possible cause of spots and discoloration after copper plating, but cautions that the problem may have more than one cause. The reply emphasizes that a single diagnosis is rarely possible from the symptom alone, comparing it to asking a doctor to identify a fever’s exact cause without more information. The answerer asks Jay to provide a photo of the spots and more details about the process so the forum can narrow down the cause and offer a more definitive recommendation. The thread therefore points to bleedout as a likely suspect, but not a confirmed root cause.