A monitoring method for stray current corrosion of subway metal structures based on optical fiber sensing

Abstract

The invention relates to an optical fiber sense based subway metal structure stray current corrosion monitoring method, belonging to a metal structure corrosion monitoring method. The monitoring method is that light emitted from an ASE (Amplified Spontaneous Emission) broadband light source is respectively transmitted to a polarization controller and a 2*1 optical fiber coupler through a 1*2 optical fiber coupler, wherein the polarization controller is connected with an optical fiber current sensing head incident fiber; an optical fiber current sensing head tail fiber is connected with a polarization maintaining optical fiber which has been written into a long-period optical fiber grating; the output terminal of the 2*1 optical fiber coupler is connected with an optical fiber which has been written into a first Bragg grating with a wavelength of lambda1 and then connected with an optical fiber corrosion sensing head incident fiber; and an optical fiber corrosion sensing head tail fiber is connected with the optical fiber which has been written into a second Bragg grating with a wavelength of lambda2. A sensing method comprises the following steps of: respectively transmitting light outputted from a light source into the optical fiber current sensing head and the optical fiber corrosion sensing unit; winding a sensing optical fiber on a structural steel bar loading with stray currents in a current sensing region; and a modifying Fe-C alloy film outside a conductive metal film layer by using an electrochemical method. The monitoring method provided by the invention has the advantages of using full optical fiber transmission, simple light path and good insulation property.

Description

[0001] technical field [0002] The invention relates to a method for monitoring metal structure corrosion, in particular to a method for monitoring stray current corrosion of subway metal structures based on optical fiber sensing. Background technique [0003] There are two reasons for the corrosion of subway metal structures, the first is natural corrosion, and the second is stray current corrosion. A large number of studies have shown that the degree of stray current corrosion of subway metal structures is far greater than that of natural corrosion, so the corrosion monitoring of subway metal structures is mainly aimed at the monitoring of subway stray current corrosion. The subway basically adopts the DC traction power supply method of the running rail backflow. This backflow method will inevitably have the leakage of stray current. Due to the effect of the stray current, it will cause the buried metal to produce electrolytic corrosion. It is called stray current corros...

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Problems solved by technology

[0004] At present, the method of monitoring the stray current corrosion of subway in various countries in the world is to adopt the standard half-cell potential method. In the early stage of subway construction, a permanent reference electrode (long-term Cu / CuSO4) is buried, and the distance between the buried metal structure and the reference electrode is measured. The potential difference is used to reflect the disturbance and corrosion of the stray current in the subway. The following problems exist in this method: (1) Metal corrosion is a long-term cumulative result, and the long-term reference electrode has a limited life. After several years, its measurement effect will be affected. (2) Since concrete is a porous structure with a certain degree of permeability, the key to long-term stability of the potential of the buried reference electrode is to have suitable ion-enriching fillers and the surrounding environment that is suitable for electrode work and can prevent drying, otherwise , the long-term stability of the reference electrode potential is poor, and it is very difficult to keep the reference electrode dry-proof for many years; (3) There is an IR drop in the monitoring of the polarization potential, and the existence of the IR drop will cause polarization The measurement of the potential brings errors. When there is a stray current disturbance, it is difficult to eliminate the influence of the IR drop

For the monitoring of stray current corrosion, it is required to monitor the distribution of stray current in buried metal pipelines and steel bars of concrete main structure, and to monitor the corrosion degree at the same time. The current monitoring methods and means are difficult to achieve.

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