Galvanic corrosion of magnesium alloy and aluminum alloy by kelvin probe

Abstract

Galvanic corrosion on samples of AZ91D magnesium alloy coupled with 2A12 aluminum alloy during neutral salt spray test was investigated. The variations of the surface potential were measured using scanning kelvin probe (SKP). The results showed that galvanic effect on the corrosion of AZ91D magnesium alloy is closely related to the potential difference between the anodic and cathodic materials. In the initial period, corrosion only occurred in a narrow area at the coupling interface because of the limited distance galvanic current. Then, the corrosion rate of 2A12 aluminum alloy was accelerated due to its poor stability in strong alkali environment, which was attributed to the strong alkalization caused by the corrosion of AZ91D magnesium alloy. With the increase of the potential of 2A12 aluminum alloy as a result of the continuous covering of corrosion products, the potential difference between the two materials was enlarged, which enhanced the galvanic corrosion.

Keywords

magnesium alloy / aluminum alloy / galvanic corrosion / scanning kelvin probe / salt spray test

References

[1] Song G L, Atrens A. Understanding Magnesium Corrosion a Framework for Improved Alloy Performance[J]. Advanced Engineering Materials, 2003, 5(12): 837-858.

[2] Makar G L, Kruger J. Corrosion of Magnesium[J]. International Materials Reviews, 1993, 38(3): 138-153.

[3] Song G L, St John D. Corrosion of Magnesium Alloys in Commercial Engine Coolant[J]. Materials and Corrosion, 2005, 56(1): 15-23.

[4] Jia J X, Song G L, Atrens A. Influence of Geometry on Galvanic Corrosion of AZ9ID Coupled to Steel[J]. Corrosion Science, 2006, 48(8): 2 133-2 153.

[5] Song G L, Atrens A. Corrosion Mechanism of Magnesium Alloys[J]. Advanced Engineering Materials, 1999, 1(1): 11-13.

[6] Xiao K, Dong C F, Li X G, et al. Research on Atmospheric Galvanic Corrosion Laws of Magnesium Alloys[J]. Rare Metal Materials and Engineering, 2006, 35(11): 1 716-1 719.

[7] Xiao K, Dong C F, Li X G, et al. Research on Atmospheric Galvanic Corrosion Evaluation of Magnesium Alloy[J]. Rare Metal Materials and Engineering, 2007, 36(2): 201-207.

[8] Dong C F, Xiao K, Li J Q, et al. Atmospheric Corrosion Behavior of AM60 Magnesium Alloy Coupled with Cu Alloy and Al alloy[J]. Transactions of Nonferrous Metals Society of China, 2005, 15(12): 1 938-1 944.

[9] Tong Z S, Zhang W, Li J Q, et al. Initial Laws of Atmospheric Galvanic Corrosion for Magnesium Alloys[J]. Transactions of Nonferrous Metals Society of China, 2004, 14(4): 554-561.

[10] Song G L, Johannesson B, Hapugoda S, et al. Galvanic Corrosion of Magnesium Alloy AZ91D in Contact with an Aluminium Alloy, Steel and Zinc[J]. Corrosion Science, 2004, 46(4): 955-977.

[11] Stratmann M. The Investigation of the Corrosion Properties of Metals Covered With Adsorbed Electrolyte Layers a New Experimental Technique[J]. Corrosion Science, 1987, 27(8): 869-872.

[12] Stratmann M, Streckel H. On the Atmospheric Corrosion of Metals which are Covered with Thin Electrolyte Layers-I. Verification of the Experimental Technique[J]. Corrosion Science, 199, 30 (6-7): 681-696

[13] Stratmann M, Streckel H. On the Atmospheric Corrosion of Metals Which are Covered with Thin Electrolyte Layers-II. Experimental Results[J]. Corrosion Science, 1990, 30(6-7): 697-714.

[14] Stratmann M, Streckel H. On the Atmospheric Corrosion of Metals which are Covered with Thin Electrolyte Layers-? the Measurement of Polarisation Curves on Metal Surfaces which are Covered by Thin Electrolyte Layers[J]. Corrosion Science, 1990, 30(6-7): 715-734.

[15] Tahara, Akira, Kodama Potential Distribution Measurement in Galvanic Corrosion of Zn/Fe Couple by Means of Kelvin Probe[J]. Corrosion Science, 2000, 42(4): 655-673.

[16] Song G L, Atrens A S, John D, et al. The Electrochemical Corrosion of Pure Magnesium in 1 M NaCl[J]. Corrosion Science, 1997, 39(5): 855-875.

[17] Elola A S, Otero T F, Porro A. Evolution of the Pitting of Aluminum Exposed to the Atmosphere[J]. Corrosion, 1992, 48(10): 854-863.

[18] Graedel T E. Corrosion Mechanisms for Aluminum Exposed to the Atmosphere[J]. Journal of the Electrochemical Society, 1989, 136(4): 204-212.

[19] Grundmeier G, Schmidt W, Stratmann M. Corrosion Protection by Organic Coatings: Electrochemical Mechanism and Novel Methods of Investigation[J]. Electrochim Acta, 2000, 45(15/16): 2 515-2 533.