Type 316L (UNS(1) S31603) sintered stainless steels were produced in a continuous industrial furnace at 1180°C using a dissociated ammonia atmosphere. Copper was used as an alloying element in different percentages (2, 4, 9%). The compacting pressure and the sintering time were varied in order to study their combined effect on the electrochemical behavior of the sintered stainless steels in a borate buffer solution with and without Cl− ions.
Contrary to the behavior in a sulfuric acid solution, the passivation curves are not noticeably affected by the chromium nitrides precipitation; in fact, in the borate buffer solution at pH = 8.7, iron undergoes spontaneous passivation. The interconnected porosity shape and amount become the most important parameters and copper alloying does not improve the sintered stainless steel electrochemical behavior.
In the Cl−-containing solutions, copper seems to favor the localized attack resistance, probably as a consequence of the formation of protective corrosion products.
