Galvanic table

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Galvanic corrosion

Galvanic series relationships are useful as a guide for selecting metals to be joined, will help the selection of metals having minimal tendency to interact galvanically, or will indicate the need or degree of protection to be applied to lessen the expected potential interactions. In general, the further apart the materials are in the galvanic series, the higher the risk of galvanic corrosion, which should be prevented by design. Conversely, the farther one metal is from another, the greater the corrosion will be. However, the series does not provide any information on the rate of galvanic corrosion and thus serves as a basic qualitative guide only.

The use of the galvanic series has to be done with caution and a basic knowledge of the environments that is a necessary part of this serious form of corrosion. The following documents provide different points of view regarding the ranking of metals and coatings in practical schemes for preventing galvanic corrosion.

Galvanic Table

The following galvanic table lists metals in the order of their relative activity in seawater environment. The list begins with the more active (anodic) metal and proceeds down the to the least active (cathodic) metal of the galvanic series. A "galvanic series" applies to a particular electrolyte solution, hence for each specific solution which is expected to be encountered for actual use, a different order or series will ensue. In a galvanic couple, the metal higher in the series (or the smaller) represents the anode, and will corrode preferentially in the environment. Listed below is the latest galvanic table from MIL-STD-889 where the materials have been numbered for discussion of characteristics. However, for any combination of dissimilar metals, the metal with the lower number will act as an anode and will corrode preferentially.

Active (Anodic)

  1. Magnesium
  2. Mg alloy AZ- 31B
  3. Mg alloy HK-31A
  4. Zinc (hot-dip, die cast, or plated)
  5. Beryllium (hot pressed)
  6. Al 7072 clad on 7075
  7. Al 2014-T3
  8. Al 1160-H14
  9. Al 7079-T6
  10. Cadmium (plated)
  11. Uranium
  12. Al 218 (die cast)
  13. Al 5052-0
  14. Al 5052-H12
  15. Al 5456-0, H353
  16. Al 5052-H32
  17. Al 1100-0
  18. Al 3003-H25
  19. Al 6061-T6
  20. Al A360 (die cast)
  21. Al 7075- T6
  22. Al 6061-0
  23. Indium
  24. Al 2014-0
  25. Al 2024-T4
  26. Al 5052-H16
  27. Tin (plated)
  28. Stainless steel 430 (active)
  29. Lead
  30. Steel 1010
  31. Iron (cast)
  32. Stainless steel 410 (active)
  33. Copper (plated, cast, or wrought)
  34. Nickel (plated)
  35. Chromium (Plated)
  36. Tantalum
  37. AM350 (active)
  38. Stainless steel 310 (active)
  39. Stainless steel 301 (active)
  40. Stainless steel 304 (active)
  41. Stainless steel 430 (active)
  42. Stainless steel 410 (active)
  43. Stainless steel 17-7PH (active)
  44. Tungsten
  45. Niobium (columbium) 1% Zr
  46. Brass, Yellow, 268
  47. Uranium 8% Mo
  48. Brass, Naval, 464
  49. Yellow Brass
  50. Muntz Metal 280
  51. Brass (plated)
  52. Nickel-silver (18% Ni)
  53. Stainless steel 316L (active)
  54. Bronze 220
  55. Copper 110
  56. Red Brass
  57. Stainless steel 347 (active)
  58. Molybdenum, Commercial pure
  59. Copper-nickel 715
  60. Admiralty brass
  61. Stainless steel 202 (active)
  62. Bronze, Phosphor 534 (B-1)
  63. Monel 400
  64. Stainless steel 201 (active)
  65. Carpenter 20 (active)
  66. Stainless steel 321 (active)
  67. Stainless steel 316 (active)
  68. Stainless steel 309 (active)
  69. Stainless steel 17-7PH (passive)
  70. Silicone Bronze 655
  71. Stainless steel 304 (passive)
  72. Stainless steel 301 (passive)
  73. Stainless steel 321 (passive)
  74. Stainless steel 201 (passive)
  75. Stainless steel 286 (passive)
  76. Stainless steel 316L (passive)
  77. AM355 (active)
  78. Stainless steel 202 (passive)
  79. Carpenter 20 (passive)
  80. AM355 (passive)
  81. A286 (passive)
  82. Titanium 5A1, 2.5 Sn
  83. Titanium 13V, 11Cr, 3Al (annealed)
  84. Titanium 6Al, 4V (solution treated and aged)
  85. Titanium 6Al, 4V (anneal)
  86. Titanium 8Mn
  87. Titanium 13V, 11Cr 3Al (solution heat treated and aged)
  88. Titanium 75A
  89. AM350 (passive)
  90. Silver
  91. Gold
  92. Graphite

End - Noble (Less Active, Cathodic)

Galvanic Compatibility

Often when design requires that dissimilar metals come in contact, the galvanic compatibility is managed by finishes and plating. The finishing and plating selected facilitate the dissimilar materials being in contact and protect the base materials from corrosion.

  • For harsh environments, such as outdoors, high humidity, and salt environments fall into this category. Typically there should be not more than 0.15 V difference in the "Anodic Index". For example; gold - silver would have a difference of 0.15V being acceptable.
  • For normal environments, such as storage in warehouses or non-temperature and humidity controlled environments. Typically there should not be more than 0.25 V difference in the "Anodic Index".
  • For controlled environments, such that are temperature and humidity controlled, 0.50 V can be tolerated. Caution should be maintained when deciding for this application as humidity and temperature do vary from regions.

Anodic Index

Metallurgy

Gold, solid and plated, Gold-platinum alloy 0.00

Rhodium plated on silver-plated copper 0.05

Silver, solid or plated; monel metal. High nickel-copper alloys 0.15

Nickel, solid or plated, titanium an s alloys, Monel 0.30

Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high copper-nickel alloys; nickel-chromium alloys 0.35

Brass and bronzes 0.40
High brasses and bronzes 0.45
18% chromium type corrosion-resistant steels 0.50

Chromium plated; tin plated; 12% chromium type corrosion-resistant steels 0.60

Tin-plate; tin-lead solder 0.65

Lead, solid or plated; high lead alloys 0.70
Aluminium, wrought alloys of the 2000 Series 0.75

Iron, wrought, gray or malleable, plain carbon and low alloy steels 0.85

Aluminium, wrought alloys other than 2000 Series aluminium, cast alloys of the silicon type 0.90

Aluminium, cast alloys other than silicon type, cadmium, plated and chromate 0.95

Hot-dip-zinc plate; galvanized steel 1.20

Zinc, wrought; zinc-base die-casting alloys; zinc plated 1.25

Magnesium & magnesium-base alloys, cast or wrought 1.75

Beryllium

Galvanic Series in Seawater

A galvanic series has been drawn up for metals and alloys in seawater, which shows their relative nobility. The series is based on corrosion potential measurements in seawater. The relative position of the materials can change in other environments. The further apart the materials are in this series, the higher the risk of galvanic corrosion.

Most cathodic, noble, or resistant to corrosion

  • Platinum
  • Gold
  • Graphite
  • Titanium
  • Silver
  • Chlorimet 3
  • Hastelloy C
  1. 18-8 Mo stainless steel (passive)
  2. 18-8 stainless steel (passive)
  3. Chromium steel >11 % Cr (passive)
  4. Inconel (passive)
  5. Nickel (passive)
  6. Silver solder
  7. Monel
  8. Bronzes
  9. Copper
  10. Brasses
  • Chlorimet 2
  • Hastelloy B
  • Inconel (active)
  • Nickel (active)
  • Tin
  • Lead
  • Lead-tin solders
  • 18-8 Mo stainless steel (active)
  • 8-8 stainless steel (active)
  • Ni-resist
  • Chromium steel >11 % Cr (active)
  1. Cast iron
  2. Steel or iron
  3. 024 aluminum
  4. Cadmium
  5. Commercially pure aluminium
  6. Zinc
  7. Magnesium and its alloys

Most anodic or easy to corrode

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