Conditions and main influencing factors of the thermocouple corrosion is analysed

Thermocouple when use shall be properly protected well, most people think that the product in the case of can use need not tube, actually this kind of idea is wrong. Because there are many uncertain factors will affect the use of our products. Such as thermocouple will corrosion situation is in use process, these problems we three chang in the roughly to analyse. Thermocouple have two different metals in solution, direct contact because of the different constitutes a corrosion cell electrode potential, electrode potential is more negative metal dissolve corrosion, the corrosion as galvanic corrosion, corrosion, or contact bimetallic corrosion.

thermocouple corrosion conditions:

1) Two different metal in solution of direct contact; （ Solution)

2) Two different metal electrode potential difference; （ Potential factors)

3) Two different metal decorate a space between the thermocouple ( The geometric factors) 。

one less factors thermocouple corrosion conditions are not established.

thermocouple corrosion, but also into a double metal corrosion or metal contact corrosion. Is made up of a less active metal ( The cathode) And a more active metal ( Anode) Contact in electrolyte solution, the current caused by constitute a galvanic corrosion, resulting in low potential of metal ( Anode) Higher metal corrosion speed increases, the potential ( The cathode) The phenomenon of corrosion speed. In this process, the cathode is under the protection of the anode. Anode area ratio increase, medium conductivity decreases, and aggravate the anode corrosion.

the thermocouple corrosion conditions:

1) Thermocouple corrosion depends on the electrode potential difference between dissimilar metals in the first place. The potential difference refers to the two metals in electrolyte solution ( Corrosive medium) The actual potential, and the corrosion potential of metals in the solution, rather than the standard electrode potential of metal or equilibrium potential; Engineering must be two kinds of metal materials in contact, can choose according to the measured galvanic sequence are relatively close to metal material to reduce the potential difference, in order to reduce the galvanic corrosion.

2) The electrical conductivity of corrosion medium; Through conducting corrosive medium, mutual contact of dissimilar metal corrosion can form a complete circuit.

3) Metal polarization and due to Yin and anode reaction on the surface of the surface coating or the influence of the corrosion products;

4) The space between the thermocouple placement ( The geometric factors) 。

thermocouple corrosion of the main influence factors:

1) Form a thermocouple to the potential difference between the metal, the potential difference between the two kinds of metal value, the greater the galvanic corrosion tend to be more serious;

2) Electricity to Yin and anode area ratio. This is the very important factors influencing the galvanic corrosion tendency; In general, as the galvanic corrosion battery anode area decrease, cathode area increase, namely the increase of the cathode to anode area of the corrosion rate of anode metal increases, the more obvious. In terms of corrosion protection, must as far as possible to avoid big small cathode/anode.

3) Medium

the influence of the directly affect the stability of the metal by the medium conditions, and the change trend of all kinds of the metal is not the same. After the medium conditions change, also electrode potential reversal may occur, which changes the polarity of the metal. In addition, solution temperature, the change of composition and pH value on the influence of galvanic corrosion is very big, can also cause the polarity reversal. Some dissimilar metal contact, resting in the medium, the galvanic corrosion is not obvious, but in the case of medium flow, galvanic corrosion.

prevent/mitigate corrosion of thermocouple:

1) Select electrode potential in a work environment as far as possible close to ( Had better not exceed 50 millivolts) Metal as a contact to. The choice of more reliable basis is to refer to the actual material in a particular medium galvanic sequence data. Can be measured when necessary.

2) Avoid big small cathode anode & ndash; — Reduce the positive electrode potential metal area and try to make the electrode potential negative metal surface area increased. For example, in the practical application, it is important to pay special attention to the connecting bolt or rivet material must be the material of fitting is better than, or connection will break soon.

3) Try to make contact metal electrical insulating and make medium resistance increases. Generally by adding insulation gasket of implementation, the insulation glue can be light load.

4) Make full use of the protective layer, or try to plus protection potential. When choosing protection method should consider the influence of the area of law, and the influence of corrosion products, etc.

no matter what the product actually, use the time to do protective measures, only we do careful maintenance of product, the product will also feedback us, use more long ~