Materials Performance

MAY 2015

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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33 NACE INTERNATIONAL: VOL. 54, NO. 5 MATERIALS PERFORMANCE MAY 2015 All of the piles of each CP unit are con- nected together electrically by the special reinforcing steels. Two anodes are installed on each of the 303 piles, for a total of 606 anodes. In the trestle bridge, two Type III anodes are installed on each of the 134 piles. There are a total of 268 anodes. Measurement Results of Cathodic Protection Potentials of Steel Tubular Piles CP potentials of the piles were mea- sured using a digital multimeter and por- table silver/silver chloride (Ag/AgCl) sea- water reference electrode. Potentials were measured at the two piles of each bent in the w harf platform , single piles of the water-collecting Wells A and B, and one pile of each bent in the trestle bridge. Each pile has three measurement points: at the surface of the water, in the submerged zone, and on the seabed. Figure 1 shows the CP potentials of the piles in the wharf platform and water- collecting wells. O verall , CP potentials (with respect to Ag/AgCl) are between –900 and –952 mV, with potentials between –901 and –950 mV at the surface of the water, between –901 and –951 mV in the sub- merged zone, and between –900 and –952 mV at the seabed. TABLE 1. REQUIREMENTS OF ANODE ELECTROCHEMICAL PROPERTIES Open Potential (V vs. SCE) Work Potential (V vs. SCE) Practical Capacity (A·h/kg) Current Effciency (%) Consumption Rate (kg/A·y) Dissolution Condition –1.18 ~ –1.10 –1.12 ~ –1.05 ≥2,600 ≥90 3.37 Corrosion products fall off easily and anode surfaces dissolve uniformly TABLE 2. SIZE AND WEIGHT OF THE ANODES Type Size (mm) Weight (kg) I 1200 × (170+200) × 180 105 II 1150 × (170+200) × 180 100.5 III 900 × (190+215) × 180 98 TABLE 3. CP UNIT AND ARRANGEMENT OF ANODES CP Unit Location of Steel Tubular Piles Quantity of Steel Tubular Piles Anode Type 1 Wharf platform Bent 1 - 9 58 Type II 2 Bent 10 - 18 48 Type II 3 Bent 19 - 27 50 Type I 4 Bent 28 - 35 44 Type I 5 Bent 36 - 43 44 Type I 6 Bent 44 - 51 45 Type I 7 Water-collecting Well A 6 Type II 8 Water-collecting Well B 8 Type I FIGURE 1 CP potentials at the wharf platform and water-collecting wells. Figure 2 shows the CP potentials of the piles at the trestle bridge. O verall , CP potentials are between –933 and –993 mV, with potentials between –934 and –993 mV at th e sur fa c e of th e w at er, b e tw e en –933 and –991 mV in the submerged zone, and between –934 and –992 mV at the seabed. CP potentials wholly satisfy the require- ment of the related CP standard and are

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