4BISHOP C V, THOMAY M J, PAGE B J. Black chromium-containing conversion coatings on zinc-nickel and zinc-iron alloys: US, 5415702 [P]. 1995-05-16.
5ROMAN L, BLIDARIU M, CRISTESCU C, et al. Study of conversion coatings on zinc deposition obtained from low pollution solutions [J]. Transactions of the Institute of Metal Finishing, 1997, 75 (5): 171-174.
6BIDDULPH C F, DIADDARIO L L JR, MARZANO M, et al. Black trivalent chromium chromate conversion coating: US, 2004/0156999 [P]. 2004-08-12.