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How to solve the discoloration of copper strip

Update:29-12-2020
Summary:

(1) Ensure that the copper strip is dry. Partially seal […]

(1) Ensure that the copper strip is dry. Partially seal the coiling outlet of the air cushion furnace, and use a dehumidifier and air conditioner in the partially enclosed device to control the humidity and temperature of the copper strip during coiling within a certain range.

 

(2) Control the conductivity of pure water. Control the conductivity of pure water, that is, control the content of harmful substances such as chloride ions in pure water. Generally, it is safer to control the conductivity below 50μS/cm.

 

 

(3) Control the conductivity of hot cleaning water and passivating agent. The increase in conductivity of hot cleaning water and passivation agent is mainly due to the residual acid being brought in by the running copper belt. Therefore, under the condition of ensuring the quality of pure water for cleaning, controlling the conductivity is also controlling the amount of residual acid. According to many experiments, it is safe to control the conductivity of the hot cleaning water and passivation agent below 200μS/cm.

(4) Control the concentration of acid solution during pickling.In the case of washing away the oxide layer on the surface of the annealed copper strip, a high acid concentration has no meaning. On the contrary, if the concentration is too high, the residual acid adhering to the surface of the copper strip is not easy to wash off, and accelerates the pollution of the cleaning water, causing the concentration of the residual acid in the cleaning water to be too high, causing the copper strip after cleaning to be more easily discolored. Therefore, when determining the concentration of the pickling solution, the principle should be followed: on the premise that the oxide layer on the surface of the copper strip can be cleaned, the concentration should be reduced as much as possible.

(5) Passivation with passivating agent. Most copper processing plants now use benzotriazole or BTA (molecular formula: C6H5N3) as a passivation agent. Practice has proved that it is a convenient, economical and practical passivation agent. When the copper tape passes through the BTA solution, the oxide film on the surface reacts with BTA to form a dense complex, which protects the copper matrix.

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