Effect of Copper on Active Dissolution and Pitting Corrosion of 25% Cr Duplex Stainless Steels

Abstract

Electrochemical studies were made of the influence of Cu on pitting behavior and active dissolution of 25% Cr duplex stainless steels (DSS) in chloride-containing neutral and acid solutions. Alloys with increased Cu content showed higher pitting potentials (E p ) in 1 M hydrochloric acid (HCl) and 3.5% sodium chloride (NaCl) solutions. In HCl, the current density in the active state also was lower for the Cu-containing alloys. However, the critical pitting temperature (CPT) in ferric chloride (FeCl 3 ) was not improved significantly by addition of Cu. Pitting in all environments took place preferentially in the ferrite phase. FIGURE 4. Comparison of polarization curves for high-Cu and low-Cu DSS in 1 M HCl at 65°C.FIGURE 5. Comparison of polarization curves for high-Cu, low-Cu, and nil-Cu DSS in 1 M HCl at 70°C.FIGURE 6. Comparison of polarization curves for high-Cu and low-Cu DSS in 3.5% NaCl at 65°C.FIGURE 7. Comparison of polarization curves for high-Cu, low-Cu, and nil-Cu DSS in 3.5% NaCl at 70°C.

Effect of Tungsten on the Pitting and Crevice Corrosion Resistance of Type 25Cr Super Duplex Stainless Steels

“…Researchers have found that Cu additions to SDSS increase pitting potential and overall localized corrosion resistance to halide environments. 61,64 It may be questioned, therefore, whether the difference in Cu could be responsible for the outstanding resistance of UNS S39274.…”

“…Selective phase dissolution is common in DSS. [61][62] The preferential attack depends primarily on the partitioning of alloying elements to austenite or ferrite, 61,[63][64] which in turn defines the critical localized corrosion potential of the phase (and the local PRE). 65 The phase with the lowest critical localized corrosion potential dissolves first and determines the alloy's overall pitting or crevice potentials.…”

“…Garfias-Mesias and Sykes64 and Garfias-Mesias, et al,61 conducted extensive investigations on Cu-modified SDSS using a variety of electrolytes and electrochemical techniques. The authors have shown that the extent to which Cu improves localized corrosion resistance strongly depends on the partitioning of the main alloying elements during solution annealing.…”

The Role of Copper on the Crevice Corrosion Behavior of Nickel-Chromium-Molybdenum Alloys in Aggressive Solutions

“…[8][9][10][11][12][13][14][15] One approach to improve the localized corrosion resistance of these alloys is to add small amounts of Cu. The effect of Cu addition on corrosion resistance, particularly localized corrosion, has been studied in detail for stainless steel (SS) [16][17][18][19][20][21][22][23][24][25][26][27][28] and to a lesser extent aluminum alloys. [29][30][31] However, to date, no focused study of the effect of Cu on the localized corrosion of Ni-Cr-Mo alloys has been published and the question remains as to whether its addition provides any value.…”

Коррозионное растрескивание под напряжением металлов и сплавов в агрессивных H-=SUB=-2-=/SUB=-S-CO-=SUB=-2-=/SUB=--Cl-=SUP=---=/SUP=- средах

“…Коррозионное поведение, в том числе и питтинговая коррозия дуплексных сталей зависят от термообработки, микроструктуры, степени легирования, степени деформации [42][43][44][45][46][47][48] и т. д. Дуплексные стали отжигаются в области температур 600−1200 • C; во время отжига меняется соотношение α : γ-фаз и, кроме того, фазы обогащаются разными элементами. Cr и Mo обогащают ферритную α-фазу, а Ni, Mn и N -аустенитную γ-фазу, что сказывается как на общую, так и на локализованную коррозию [49].…”