Method and apparatus for corrosion inhibition

Patent metadata

Field	Value
Publication number	US-2016289846-A1
Application number	US-201615085349-A
Country	US
Kind code	A1
Filing date	Mar 30, 2016
Priority date	Mar 31, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

The invention relates to a method for improved corrosion inhibition of metal in a system, in which system the metal is in contact with water, and a corrosion inhibitor inhibits a corrosion of the metal, wherein a voltage is applied between the metal and an auxiliary electrode, which voltage changes time-dependently after being switched on and before being switched off within a passivation region of the metal in said corrosion inhibitor, the passivation region being a region of voltage in which the corrosion inhibitor effects an inhibition of corrosion of the metal.

First claim

1 . Method for improved corrosion inhibition of metal in a system, in which system the metal is in contact with water, and a corrosion inhibitor inhibits a corrosion of the metal,
wherein a voltage is applied between the metal and an auxiliary electrode, which voltage changes time-dependently after being switched on and before being switched off within a passivation region of the metal in said corrosion inhibitor, the passivation region being a region of voltage in which the corrosion inhibitor effects an inhibition of corrosion of the metal.

2 . Method according to claim 1 , wherein the voltage is always smaller than the pitting voltage of the metal in the corrosion inhibitor solution, the pitting voltage being the lowest voltage at which pitting occurs in the metal in the corrosion inhibitor solution.

3 . Method according to claim 1 , wherein the passivation region is a region in which stable pitting corrosion of the metal does not occur when the metal is in contact with said corrosion inhibitor solution.

4 . Method according to claim 1 ,
wherein the voltage is a swept voltage or a pulsed voltage or a voltage having a waveform, preferably a saw tooth form.

5 . Method according to claim 1 ,
wherein the voltage changes at a rate of greater or equal 0.5 mV/s, preferably greater or equal 0.7 mV/s and/or lower or equal 2 mV/s, preferably lower or equal 1.5 mV/s, preferably of 1 mV/s.

6 . Method according to claim 1 ,
wherein the voltage has a modulated frequency with alternated negative and positive whole cycles or positive cycles or negative cycles.

7 . Method according to claim 1 ,
wherein the maximum voltage applied is 0.4 V, preferably 0.3 V, preferably 0.25 V, preferably 0.15 V, preferably 0.1 V, preferably 0.08V.

8 . Method according to claim 1 ,
wherein the minimum voltage applied is −0.8 V, preferably −0.4 V, preferably −0.2 V, preferably −0.15V.

9 . Method according to claim 1 ,
wherein the voltage sweeps between the minimum voltage and the maximum voltage at least 2 times, preferably at least 4 times, preferably at least 6 times.

10 . Method according to claim 1 ,
wherein the metal is in a first step brought in contact with the corrosion inhibitor solution, and the voltage is applied in a second step after the first step, in which second step the metal had contacted the corrosion inhibitor solution and is no longer in contact with the corrosion inhibitor solution.

11 . Method according to claim 1 ,
wherein, while the metal is in contact with the dissolved corrosion inhibitor, a voltage, preferably a swept voltage, is applied which preferably varies within the passivation range for the metal in the corrosion inhibitor, preferably between −0.8 V and +0.4 V.

12 . Method according to claim 1 ,
wherein the corrosion inhibitor comprises or consists of Benzotriazole, BTA, or a derivative of Benzotriazole, or a mixture of Benzotriazole, BTA, and Triethanolamine, TEA, or a mixture of a derivative of Benzotriazole and Triethanolamine, wherein preferably the corrosion inhibitor does not contain a solvent except for water.

13 . Method according to claim 1 ,
wherein the metal is metal of a metal piping system or a closed loop heating system, and/or the water is tap water.

14 . Method according to claim 1 ,
wherein the metal is metal of a piping system comprising at least one pipe, and wherein the auxiliary electrode is at least partially formed as a wire running through the at least one pipe.

15 . Method according to claim 14 ,
wherein the auxiliary electrode formed as a wire is held at a distance to an inner wall of the pipe by at least one or a plurality of spacers, and wherein the at least one spacer is a polytetrafluoroethylene sphere having a diameter equal to or smaller than an inner diameter of the pipe through which the wire is running.

16 . Method according to claim 1 ,
wherein the auxiliary electrode comprises or consists of copper and/or titanium.

17 . Method according to claim 1 ,
wherein a voltage due to corrosion between the metal and the auxiliary electrode is measured and the voltage applied between the metal and an auxiliary electrode is switched on when said voltage due to corrosion is greater than a predefined threshold.

18 . Method according to claim 1 ,
wherein the method is employed to remedy existing corrosion.

19 . Apparatus for inhibiting corrosion of metal in a system, in which system the metal is in contact with water, and a corrosion inhibitor inhibits a corrosion of the metal, comprising means for applying a voltage between the metal and an auxiliary electrode, such that said voltage changes time-dependently after being switched on and before being switched off within a passivation region of the metal in said corrosion inhibitor, the passivation region being a region of voltage in which the corrosion inhibitor effects an inhibition of corrosion of copper when the meal is in contact with said corrosion inhibitor.

20 . Apparatus according to claim 19 , wherein the apparatus is adapted for performing a method for improved corrosion inhibition of metal in a system, in which system the metal is in contact with water, and a corrosion inhibitor inhibits a corrosion of the metal, wherein a voltage is applied between the metal and an auxiliary electrode, which voltage changes time-dependently after being switched on and before being switched off within a passivation region of the metal in said corrosion inhibitor, the passivation region being a region of voltage in which the corrosion inhibitor effects an inhibition of corrosion of the metal.

Assignees

• Mitsubishi Electric Corp

Inventors

• Bi Huichao
• Burstein Gordon Timothy
• Kawaley Georgeanna

Classifications

• C23F13/20 Primary

  Conducting electric current to electrodes · CPC title

• C23F13/22

  Monitoring arrangements therefor · CPC title

• C02F1/4602 Primary

  for prevention or elimination of deposits · CPC title

• C02F2307/14

  Treatment of water in water supply networks, e.g. to prevent bacterial growth · CPC title

• C23F11/10

  using organic inhibitors · CPC title