Performance of Corrosion-Resistant Alloys in Concentrated Acids

doi:10.1007/s40195-017-0538-y

Abstract

Abstract:

Nickel alloys containing optimum amounts of chromium (Cr), molybdenum (Mo) and tungsten (W) are widely used in the chemical processing industries due to their tolerance to both oxidizing and reducing conditions. Unlike stainless steel (SS), Ni-Cr-Mo (W) alloys exhibit remarkably high uniform corrosion resistance in major concentrated acids, like hydrochloric acid (HCl) and sulfuric acid (H₂SO₄). A higher uniform corrosion resistance of Ni-Cr-Mo (W) alloys, compared to other alloys, in concentrated acids can be attributed to the formation of protective oxide film of Mo and W in reducing acids, and Cr oxide film in oxidizing solutions. The localized corrosion resistance of Ni-Cr-Mo (W) alloys, containing high amount Cr as well as Mo (or Mo + W), is also significantly higher than that of other commercially available alloys. The present study investigates the role of alloying elements, in nickel alloys, to uniform corrosion resistance in concentrated acids (HCl, HCl + oxidizing impurities and H₂SO₄) and localized corrosion performance in chloride-rich environments using ASTM G-48 test methodology. The corrosion tests were conducted on various alloys, and the results were analyzed using weight loss technique and electrochemical techniques, in conjunction with surface characterization tools.

Key words: Nickel-chromium-molybdenum-tungsten, Corrosion-resistant alloys, Reducing acid, Oxidants, Localized corrosion, Surface characterization

Ajit Mishra. Performance of Corrosion-Resistant Alloys in Concentrated Acids[J]. Acta Metallurgica Sinica (English Letters), 2017, 30(4): 306-318.

Figures/Tables 23

Table 1 Weight percent of major alloying elements in Ni-Cr-Mo (W) alloys

Alloys (UNS Number)	Cr	Mo	W	Cu	Ni
G-35 (N06035)	33	8			Bal.
C-2000 (N06200)	23	16		1.6	Bal.
Alloy 59 (N06059)	23	16			Bal.
C-22 (N06022)	22	13	3		Bal.
C-22HS (N07022)	21	17			Bal.
Alloy 686 (N06686)	21	16	4		Bal.
C-276 (N10276)	16	16	4		Bal.
HYBRID-BC1 (N10362)	15	22			Bal.
B-3 (N10675)	1.5	28.5			Bal.
Alloy 718 (N07718)	18	3			Bal.
Alloy 625 (N06625)	21	9			Bal.

Fig. 1 Microstructures of mill-annealed a C-2000, b G-35, c HYBRID-BC1, d B-3 alloys

Fig. 2 Iso-corrosion diagram of B-3 alloy in HCl solution

Fig. 3 Iso-corrosion diagram of HYBRID-BC1 alloy in HCl solution

Fig. 4 Iso-corrosion diagram of C-276 alloy in HCl solution

Fig. 5 Iso-corrosion diagram of C-2000 alloy in HCl solution

Fig. 6 Iso-corrosion diagram of C-22 alloy in HCl solution

Fig. 7 Temperature calculated to induce corrosion rate of 0.1 mm/y (4 mpy) in reagent grade HCl solution

Fig. 8 Temperature calculated to induce corrosion rate of 0.5 mm/y (20 mpy) in reagent grade HCl solution

Fig. 9 Potentiodynamic polarization graphs of C-22 alloy in various concentrations of HCl acid at room temperature

Table 2 Corrosion rate of corrosion-resistant alloys in HCl solution and HCl solution containing oxidants

Alloy	20% HCl (mpy)		20% HCl + 10 ppm Fe³⁺ (mpy)		20% HCl + 100 ppm Fe³⁺ (mpy)		20% HCl + 1000 ppm Fe³⁺ (mpy)
Alloy	23 °C	52 °C	23 °C	52 °C	23 °C	52 °C	23 °C	52 °C
B-3	1.4	5.9	2.0	9.1	4.9	22.8	44.8	118.9
HYBRID-BC1	1.6	7.1	1.8	10.9	5.8	26.3	7.6	136.2
C-276	1.6	11.4	1.8	16.6	6.5	28.2	5.0	119.7
C-22	2.0	12.6	2.4	23.3	0.4	33.8	0.3	4.4
C-22HS	2.0	13.8	1.9	15.9	0.3	26.5	0.6	4.3
C-2000	2.0	14.2	2.3	22.1	0.4	2.1	0.3	1.6
G-35	6.1	31.0	7.8	46.8	0.2	58.3	0.1	1.3
Alloy 59	2.1	14.6	2.1	20.0	0.4	1.8	0.1	2.1
Alloy 686	2.2	10.4	2.0	17.1	6.6	29.0	0.5	6.3

Fig. 10 Effect of oxidants on the corrosion performance of CRA’s (temp.: 52 °C)

Fig. 11 Potentiodynamic polarization graphs of corrosion-resistant alloys in 20% HCl acid at room temperature

Fig. 12 Potentiodynamic graphs in 20% (wt%) HCl, with and without impurity, at an ambient temperature for a C-22; b HYBRID-BC1

Fig. 13 Schematic of effect of oxidants on the corrosion performance of Ni-Cr-Mo (W) alloys. Graph also shows the active and passive regions for the black curve

Fig. 14 Atomic concentration of major alloying elements obtained from XPS survey spectra for HYBRID-BC1 alloy

Fig. 15 Temperature calculated to induce corrosion rate of 0.1 mm/y (4 mpy) in reagent grade H2SO4 acid

Fig. 16 Temperature calculated to induce corrosion rate of 0.5 mm/y (20 mpy) in reagent grade H2SO4 acid

Fig. 17 Potentiodynamic polarization graphs of C-2000 alloy in various concentrations of reagent grade H2SO4 acid at room temperature

Fig. 18 Iso-corrosion diagram of HYBRID-BC1 alloy in H2SO4 acid

Fig. 19 Potentiodynamic polarization graphs of B-3 in various concentrations of reagent grade H2SO4 acid at room temperature

Fig. 20 Microstructures of C-2000 alloy after corrosion testing in 80% H2SO4 at 107 °C, a optical micrograph and b SEM image. EDX spot analysis did not show any enrichment of Mo (or its oxides) in the surface layer

Table 3 Critical pitting temperature (CPT) and critical crevice temperature (CCT) for various alloys obtained using ASTM G-48C, D test methodology (PREN,W: %Cr + 3.3 (%Mo + 0.5%W) + 16%N) [31]

Alloys	CPT (°C)	CCT (°C)	PRE_N,W
316L SS	15	0	28
Alloy 718	45	10	28
Alloy 625	85	35	51
G-35	95	45	59
C-276	>130	55	75
C-22	>130	80	70
C-2000	>130	80	76
C-22HS	>130	100	77

References

[1]	MTI Publication MS-1, Materials Selector for Hazardous Chemicals—Sulfuric Acid, Materials Technology Institute of the Chemical Process Industries Inc., 1997, ed. by C.P. Dillon
[2]	MTI Publication MS-3, Materials Selector for Hazardous Chemicals—Hydrochloric Acid, Hydrogen Chloride and Chlorine, Materials Technology Institute of the Chemical Process Industries Inc., 1999, ed. by C.P. Dillon and W.I. Pollock
[3]	W.Z. Friend, Corrosion of Nickel and Nickel-Based Alloys (Wiley, New York, 1980), p. 292
[4]	P. Crook, ASM Handbook, vol. 13B(ASM International, Materials Park, 2005), p. 228
[5]	A.C. Lloyd, J.J. Noel, S. McIntyre, D.W. Shoesmith, Electrochim. Acta 49, 3015 (2004)
[6]	P. Jakupi, F. Wang, J.J. Noel, D.W. Shoesmith, Corros. Sci. 53, 1670(2011)
[7]	A.K. Mishra, D.W. Shoesmith, Corrosion 70, 721 (2014)
[8]	J.R. Hayes, J.J. Gray, A.W. Szmodis, C.A. Orme, Corrosion 62, 491 (2006)
[9]	N.S. Meck, P. Crook, D.L. Klarstrom, Houston TX, 2004)
[10]	A.K. Mishra, D.W. Shoesmith, P.E. Manning, Corrosion (2016). doi:10.5006/2193
[11]	M. Moriya, M.B. Ives, Corrosion 40, 62 (1984)
[12]	M. Moriya, M.B. Ives, Corrosion 40, 105 (1984)
[13]	R. Qvarfort, Corros. Sci. 40, 215(1998)
[14]	K.J. Evans, A. Yilmaz, S.D. Day, L.L. Wong, J.C. Estill, R.B. Rebak, J. Met. 57, 56(2005)
[15]	X. Shan, J.H. Payer, J. Electrochem. Soc. 156, C313(2009)
[16]	N.S. Zadorozne, C.M. Giordano, M.A. Rodriguez, R.M. Carranza, R.B. Rebak, Electrochim. Acta 76, 94 (2012)
[17]	M.A. Rodriguez, R.M. Carranza, R.B. Rebak, Corrosion 66, 1 (2010)
[18]	M.R. Ortiz, M.A. Rodriguez, R.M. Carranza, R.B. Rebak, Corros. Sci. 68, 72(2013)
[19]	C.M. Giordano, M.R. Ortiz, M.A. Rodriguez, R.M. Carranza, R.B. Rebak, Corros. Engi. Sci. Technol. 46, 129(2011)
[20]	A.K. Mishra, G.S. Frankel, Corrosion 64, 836 (2008)
[21]	P. Jakupi, J.J. Noel, D.W. Shoesmith, Corros. Sci. 54, 260(2012)
[22]	N. Ebrahimi, P. Jakupi, J.J. Noel, D.W. Shoesmith, Corrosion 71, 1441 (2015)
[23]	ASTM Annual Book of Standards, Volume 03.02 Wear and Erosion, Metal Corrosion (West Conshohocken, PA) (2011)
[24]	A.K. Mishra, X. Zhang, D.W. Shoesmith, Corrosion 72, 357 (2016)
[25]	N. Sridhar, Mater. Perform. 27, 40(1988)
[26]	P. Crook, Houston TX, 1996)
[27]	P. Crook, M.L. Caruso, D.A. Kingseed, Mater. Perform. 36, 49(1997)
[28]	N. Sridhar, Houston TX, 1987)
[29]	E.L. Hibner, L.E. Shoemaker, Houston TX, 2006)
[30]	G.S. Frankel, J. Electrochem. Soc. 145, 21(1998)
[31]	Z. Szklarska-Smialowska, Pitting and Crevice Corrosion of Metals (Houston, TX, NACE International, 2005)