Letter 38006

Immersion copper coating of MIG welding wire [South Africa] 

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I am a chemical supplier to a company making copper coated welding wire. Im not a fundi on the process, however i am trying to help them with their weldability problems (burn-back and nibbling), which they originally thought was due to deposition of metals(esp manganese) on the wire before coating. The water used in the baths for Caustic, rinse, and sulphuric acid is town water with high TDS and metals. We have changed the entire bath to demin water and still get a black slimy deposit on the wire, and poor weldability. My feeling is this is not from the water but rather from drawing soaps, oils, dust etc which is not cleaned properly from the wire. Please advise on what steps to take to get to the route cause of our problem.

Steven Lea
Improchem - Johannesburg, South Africa

Your trouble seems to be popular. I don't think it is related with copper plating process. Your guess is right, it is probably caused by such residuals drawing soap, micro fine iron powder, other contaminats. But please doubt cleanliness of steel's surface. If wire rod is mechanically descaled (not acid cleaned), scale and sub-scale remain heavily. After copper plating it becomes rust. Rusty wire gets feedsability incredibly worse and causes severe abration of contact tip. If you want to check rust of finished wire, give 4.0-5.0V(+) to finished wire in 5% salt water and observe floating substance. If it looks brown, the tested wire is rusty. I hope my information will help you. Thanks

Koichi Nomura
- Kakogawa, Hyoggo, Japan

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