Seawater Corrosion

CORROSION POTENTIALS IN FLOWING SEAWATER

(V vs SCE Half-Cell Reference Electrode)

The alloys below are listed in order of the potential they exhibit in flowing seawater. The alloys marked with an asterisk may become active and exhibit a potential near -0.5 volts in low-velocity or poorly aerated water and at shielded areas.

RANGE ALLOYS

+0.3 +0.2 Graphite
+0.26 +0.18 Platinum
+0.09 0.03 Ni-Cr-Mo alloy C
+0.06 0.04 Titanium
+0.04 0.02 Nickel-Iron-Chromium alloy 825
+0.06 0.04 Alloy “20” Stainless Steels, cast & wrought
0 -0.1 *Stainless Steel – Type 316, 317 (passive)
-0.03 -0.14 Nickel-Copper alloys 400, K-500
-0.10 -0.15 Silver
-0.04 -0.10 *Stainless Steel -Types 302 304 321
347(passive)
-0.10 -0.2 Nickel 200
-0.09 -0.2 Silver Braze Alloys
-0.13 -0.18 *Nickel-Chromium alloy 600 (passive)
-0.14 -0.22 Nickel-Aluminium Bronze
-0.17 -0.24 70-30 Copper-Nickel
-0.19 -0.25 Lead
-0.20 -0.28 *Stainless Steel – Type 430 (passive)
-0.21 -0.27 80-20 Copper-Nickel
-0.22 -0.28 90-10 Copper-Nickel
-0.24 -0.28 Nickel Silver
-0.23 -0.35 *Stainless Steel – Type 410 416 (passive)
-0.24 -0.32 Tin Bronzes (G&M)
-0.25 -0.29 Silicon Bronze
-0.26 -0.34 Manganese Bronze
-0.26 -0.36 Admiralty Brass, Aluminium Brass
-0.27 -0.36 Pb-Sn Solder (50/50)
-0.30 -0.37 Copper
-0.30 -0.33 Tin
-0.31 -0.40 Naval Brass, Yellow Brass, Red Brass
-0.31 -0.40 Aluminium Bronze
-0.33 -0.46 *Stainless Steel – Type 316 317 (active)
-0.34 -0.46 *Nickel-Chromium alloy 600 (active)
-0.43 -0.54 Austentic Nickel Cast Iron
-0.44 -0.58 *Stainless Steel – Type 302 304 321 347 (active)
-0.45 -0.57 *Stainless Steel – Type 410 416 430 (active)
-0.57 -0.63 Low Alloy Steel
-0.60 -0.72 Mild Steel, Cast Iron
-0.70 -0.74 Cadmium
-0.76 -1.00 Aluminium Alloys
-0.98 -1.03 Zinc
-1.60 -1.63 MagnesiumACA EDUCATIONAL GUIDE & TECHNICAL BULLETIN