Corrosion Resistance of Injection-Molded 17-4PH Steel in Sodium Chloride Solution

Abstract

The corrosion resistance of 17-4PH powder injection-molded (PIM) martensitic stainless steel (SS) was evaluated in naturally aerated sodium chloride (NaCl) solution (3 wt%) at 25°C. This resistance was investigated by analyzing the curves of the evolution of open-circuit potential with time (E ocp vs. time), electrochemical impedance spectroscopy (EIS), and surface observation by scanning electron microscopy (SEM) at increasing times of immersion. The susceptibility to pitting was investigated using cyclic potentiodynamic polarization curves and SEM observation after polarization. Additionally, the susceptibility to intergranular corrosion was evaluated by a modifi ed procedure described in ASTM A 262 Practice A. The results of the 17-4PH PIM steel were compared to that of a 17-4PH steel produced by conventional metallurgy. The results showed that under steady-state conditions the PIM steel presented a behavior typical of passive metals during the whole test period (60 days of immersion). This was indicated by the E ocp vs. time curves, EIS results, and SEM observation of the surface at increasing periods of immersion. The steel showed a bright metallic surface and no signs of corrosion during the whole period of the test. Cyclic potentiodynamic polarization curves indicated that both 17-4PH steels, conventional and PIM, are susceptible to pitting but the PIM steel showed a slightly increased susceptibility to pitting, which was supported by posttest observation by SEM. In the PIM steel, pits seemed to be related to the porosity that had inner oxide inclusions. The 17-4PH steel, produced by both PIM technology and conventional metallurgy, did not show a susceptibility to intergranular corrosion by ASTM A 262 Practice A.

Effect of immersion time at the stainless steel 304L/NaCl (0.01 M) interface

“…Immersion time is one of the most influential parameter on interface properties. Results on stainless steel related to short-term tests have been widely discussed in literature [5][6][14][15], however little has been carried out for relatively long contact periods between the electrolyte and the metallic material [16,17].…”

Enhanced Mechanical Properties of Injection Molded 17-4PH Stainless Steel through Reduction of Silica Particles by Graphite Additions

“…10) With the presence of oxide particles, the mechanical properties and corrosion resistance of the sintered stainless steels deteriorate. 2,4,11,12) Since water atomized stainless steel powders for powder injection molding (PIM) process are typically very fine in order to attain high sintered densities, the powders contain significant amounts of SiO 2 on the surface. Thus, the elimination of SiO 2 inclusions in sintered compacts has become an important focus of research.…”

Effect of chemical passivation treatment on pitting corrosion resistance of AISI 410 and 17–4 PH stainless steels

“…The corrosion behavior has already been investigated for the AISI 410 SS, [5,9,[12][13][14][15] and for the 17-4 PH SS. [6,7,10,[16][17][18][19] Although some studies have demonstrated that the chemical passvation promoted an improvement on pitting corrosion resistance for other types of stainless steels, [20][21][22][23][24][25][26][27] it was not found studies relating this surface treatment to corrosion behavior of the AISI 410 and 17-4 PH SS's.…”

“…The chemical passivation treatment did not produce significant effect on the surface roughness Ra of the studied stainless steels. Moayed et al [6] Ground surface (1200 grit), solution 3.5% NaCl, 25°C, scan rate 0.5 mV/s vs. SCE −230 Ranging from 95 to 178 -Tavakoli [16] Solution 3.5% NaCl, room temperature, scan rate 0.05 mV/s vs. SCE −120 205 -Costa et al [19] Polished surface (diamond paste 1 µm), solution 3% NaCl, 25°C, scan rate 1 mV/s vs. SCE −310 190 −115 | 829…”