Page 255 - Corrosion Engineering Principles and Practice
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228   C h a p t e r   7              C o r r o s i o n   F a i l u r e s ,   F a c t o r s ,   a n d   C e l l s    229


                                                                 Graphite
                                                                 Platinum
                                                                 Ni-Cr-Mo-Cu-Si alloy G
                                                                 Ni-Cr-Mo alloy C
                                                                 Titanium
                                                                 Alloy 825
                                                                 Alloy 20
                                                                 316, 317 SS (passive)
                                                                 Monel 400, K-500
                                                                 Silver
                                                                 302, 304, 321, 347 SS (passive)
                                                                 Nickel 200
                                                                 Silver bronze alloys
                                                                 Alloy 600 (Passive)
                                                                 Nickel-aluminium bronze
                                                                 70–30 copper-nickel
                                                                 Lead
                                                                 430 SS (Passive)
                                                                 80–20 copper-nickel
                                                                 90–10 copper-nickel
                                                                 Nickel silver
                                                                 410, 416 SS (Passive)
                                                                 Tin bronzes (G&M)
                                                                 Silicon bronze
                                                                 Manganese bronze
                                                                 Admiralty, aluminium brasses
                                                                 Pb-Sn Solder (50/50)
                                                                 Copper
                                                                 Tin
                                                                 Naval, yellow, red brasses
                                                                 Aluminium bronze
                                                                 316, 317 SS (Active)
                                                                 Alloy 600 (Active)
                                                                 Austenitic nickel cast iron
                                                                 302, 304, 321, 347 SS (Active)
                                                                 410, 416, 430 SS (Active)
                                                                 Low alloy steel
                                                                 Mild steel, cast iron
                                                                 Cadmium
                                                                 Aluminium alloys
                                                                 Zinc
                                                                 Magnesium
                 –2       –1.5      –1       –0.5      0        0.5
                                     Potential (V vs. SCE)
                 FIGURE 7.18  Galvanic series for slow-moving seawater.
                         However, the situation can lead to the corrosion of steel when the
                      surface area of the cathode (copper) approaches that of the anode (steel)
                      such as shown in Fig. 7.20 or when the surrounding environment is
                      more conductive or corrosive in the region where the galvanic coupling
                      exists (Fig. 7.21). In the example shown in Fig. 7.20, the anodic corrosion
                      of the anchor is partly due to the galvanic corrosion cell formed by the
                                                        Cathode site
                                                     Copper water service
                            Anode site
                           Iron watermain
                                           I C        I C       I C








                      FIGURE 7.19  Underground corrosion cell involving connection of dissimilar
                      metals.
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