Effects of Copper Addition on the Passivity and Corrosion Behavior of 27Cr-7Ni Hyper Duplex Stainless Steels in Sulfuric Acid Solution

Abstract

The effect of the Cu addition on the passivation behavior of hyper duplex stainless steels in both the active and passive states was investigated using the electrochemical tests, a scanning electron microscope-energy dispersive spectroscope, a scanning Auger multi-probe analysis and an X-ray photoelectron spectroscopy analysis in sulfuric acid solution. In the active region of ¹0.2 V SCE , the Cu addition to the base alloy has a positive effect on the general corrosion resistance due to the novel Cu enriched on the surface. In the passive region of 0.6 V SCE , the Cu addition to the base alloy degraded the stability of passive film due to an increase of the formation of Cr enriched inclusion such as (Cr, Mn, Al) oxides and (Cr, Mn, Al, Fe) oxides acting as the defect in the passive film, resulting in deteriorating general corrosion resistance.

Corrosion Resistance of Cu-Alloyed Precipitation Hardenable Duplex Stainless Steel ASTM A890 Grade 1B

“…On the other hand, as shown in Figure 6(c), the samples immersed in 0.6 mol/L NaCl + 0.3 mol/L H 2 SO 4 showed a few current transients and samples immersed in 0.3 mol/L H 2 SO 4 (Figure 6(b)) showed no current transients. This result means that the addition of Cu decreased the corrosion rate in sulfuric acid solutions, a fact that is in good agreement with other works [29][30][31] . The mechanism of the improvement of corrosion resistance related to copper addition considered the formation of metallic deposits on a corroded site that hinders the anodic dissolution 8,30,31 .…”

Characterization of a Cast Duplex Stainless Steel with 3.0%Cu and Modeling of Precipitation Hardening

“…In the case of DSSs, the solution treatment is carried out at 1040°C minimum (Ref 10), followed by water cooling. Some commercial stainless steels may contain copper addition to improve corrosion resistance in non-oxidizing environments (Ref 2,(11)(12)(13)(14). UNS S32760 is an example of SDSS grade with 0.5-1.0%Cu addition to improve resistance to HCl solutions.…”

Passivation Behavior of Ce-Containing Hyper Duplex Stainless Steels in Sulfuric Acid Solution

“…Recently, Cu addition has been shown to degrade the passive film stability in DSSs because of increase in the formation of Cr oxide inclusions, which function as defect sites in the passive film, resulting in deterioration of the corrosion resistance in sulfuric acid solution. 9) The effects of Ce addition to stainless steels on the corrosion resistance in various corrosive environments have been widely reported.…”