Sodium Tungstate, Sodium Molybdate and Other Reagents Synergistic Corrosion Inhibition
- Details
- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 19:44
There’re many methods of controlling equipment corrosion in industrial cooling water system. Adding corrosion inhibitor is not only convenient, cheap, but also has strong applicability. It is one of the important methods. Common corrosion inhibitors are chromate, nitrite. Most are toxic. Sodium tungstate and sodium molybdate are non-toxic, harmless and inorganic corrosion inhibitors. It could be applied in industrial circulation water.
When adding sodium molybdate and sodium tungstate alone in the simulated cooling water, with the increase of the concentration of sodium tungstate and sodium molybdate in simulation cooling water, the corrosion rate of carbon steel gradually reduces and the corrosion rate increases. But to achieve better corrosion inhibition effect, the concentration of sodium molybdate and sodium tungstate is required quite high. In order to reduce the amount of sodium molybdate and sodium tungstate, this paper introduces the synergistic corrosion inhibition of sodium molybdate, sodium tungstate and common organic phosphoric acid (HEDP), orthophosphoric acid and Zn2+.
Through the experiment, following conclusions can be drawn:
1. In the simulated cooling water, using sodium molybdate, sodium tungstate alone requires higher concentration to have good corrosion inhibition effect on carbon steel.
2. Sodium molybdate, sodium tungstate and HEDP composite can reduce the corrosion rate of carbon steel greatly and the dosage of sodium molybdate and sodium tungstate has greatly reduced. If increasing the concentration of HEDP, corrosion inhibiton effect is more obvious, and ratio of sodium molybdate and HEDP compound sodium tungstate effect is better.
3. If instead of HEDP as part of orthophosphoric acid, then the corrosion inhibition effect is greatly increased. But if orthophosphoric acid and sodium molybdate compound using phosphoric acid concentration is greater than 4 mg/L.
4. Sodium molybdate or sodium tungstate and HEDP, Zn2+ distribution, the corrosion effect is greatly increased, the synergistic effect is obvious, to join only 0.5 mg/L Zn2+ can make corrosion highly efficient, shows good synergistic effect between the three.
5. Sodium molybdate and HEDP, orthophosphoric acid, Zn2+, cathode and anode process of carbon steel have good inhibitory effect. Sodium tungstate and HEDP, orthophosphoric acid, Zn2+, the anode process of carbon steel had good inhibitory effect. The addition of Zn2+ to cathode and anode effect is very obvious. It is a kind of excellent corrosion additives.
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