Page 202 - Corrosion Engineering Principles and Practice

176 C h a p t e r 6 R e c o g n i z i n g t h e F o r m s o f C o r r o s i o n 177

Noble Platinum
or Gold
Cathodic Graphite
Titanium
Silver
 Chlorimet 3
 Hastelloy C
 18-8 Mo Stainless Steel (Passive)
18-8 Stainless Steel (Passive)
 Chromium Steel >11% Cr (Passive)
 Inconel (Passive)
 Nickel (Passive)
 Silver Solder
Monel
Bronzes
Copper
 Brasses
 Chlorimet 2
 Hastelloy B
 Inconel (Active)
 Nickel (Active)
Tin
Lead
Lead-tin Solders
 18-8 Mo Stainless Steel (Active)
 18-8 Stainless Steel (Active)
Ni-resist
Chromium Steel >11% Cr (Active)
 Cast Iron
 Steel or Iron
2024 Aluminum
Cadmium
Active Commercially Pure Aluminium
or Zinc
Anodic Magnesium and Its Alloys

FIGURE 6.31 Galvanic series of some commercial metals and alloys
in seawater.

with the anode, the more oxygen reduction, or other cathodic reaction,
can occur and, hence, the greater the galvanic current.
From the standpoint of practical corrosion resistance, the most
unfavorable ratio is a very large cathode connected to a very small
anode. This effect is illustrated in Figs. 6.32 and 6.33. Figure 6.31
indicates that iron is anodic with respect to copper and therefore is
more rapidly corroded when placed in contact with it. This effect is
greatly accelerated if the area of the iron is small in comparison to
the area of the copper, as shown in Fig. 6.32. However, under the
reverse condition, when the area of the iron is very large compared