Measurements of hydrogen activity in iron during cathodic protection using a potentiometric concentration cell
✍ Scribed by A. Abbassi; Dr. S. B. Lyon
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- German
- Weight
- 470 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0947-5117
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✦ Synopsis
Abstract
A solid ‐ state potentiometric sensor, based on the well ‐ tried principle of the thermodynamic concentration cell, has been constructed. The sensor uses a conventional bi‐electrode design with an entry side and an exit side at which the hydrogen is detected. The sensor has been used for the quantitative determination of the hydrogen activity (equivalent H~2~ pressure) generated during cathodic protection. Thus, the background hydrogen pressure in uncharged steel is 10^−17.7^ (2 × 10^−18^ atm.) with a variation of about 20 times. During cathodic protection this value rises by large amounts. Thus, using a zinc anode, the equivalent hydrogen pressure rose by 10^10.3^ (to 4.4 × 10^−8^ atm.) in 3.5% NaCl and by 10^16.9^ (to 0.16 atm.) in artificial sea water, indicating the much larger amounts of hydrogen present in the latter case. This compares, for example, with literature data of 0.11 μA cm^−2^ and 0.60 μA cm^−2^ for hydrogen permeation at −1000 mV (SCE) in 3.5% NaCl and artificial sea water respectively. Hydrogen entry and exit was also considerably slowed in sea water. These differences are caused by local surface pH buffering and deposit formation.