Black Pad. Will heat remove the gold from an ENIG finish?
For completeness

https://blog.epectec.com/urban-legends-of-pcb-processes-enig-black-pad


  All reports and analysis point to the conditions of the nickel bath
  as the main cause of black pad, with excessive phosphorus being the
  primary issue. Affected joints are easily broken, and the corroded,
  “black” nickel is exposed, providing basis for the term "black pad".
  Even the tightest controlled production houses, which closely monitor
  all chemistry levels, temperatures and incoming raw materials, fall
  victim to this ongoing problem at some time or another


.