Summary for flux deposition rate Discussion
Flux deposition rate in galvanizing was asked in terms of dried flux thickness or grams per square meter on steel between fluxing and zinc dipping. Dr. Thomas H. Cook said he had done experiments years earlier and, while the detailed numbers were in his notebooks, he used the results to show that flux is inexpensive compared with zinc. For 12 degree Baumé flux, his final formula was flux usage equal to 0.5% of zinc usage: for every 100 kg of zinc consumed, about 0.5 kg of flux was required. He noted this assumes no purification of the flux. He also added that at 5% GZU, 100 kg of zinc would correspond to about 2,000 kg of steel galvanized. Cook further observed that using 71 °C flux and letting the steel heat up in the flux for about 3 minutes resulted in roughly twice as much flux on the steel, with a more even coating, compared with room-temperature flux.
Q. In using the pre-flux method in batch galvanizing, does anyone have any information on the thickness of the dried flux that sits on the steel between fluxing and dipping in zinc? Or perhaps the deposition rate in say grams per square meter?
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
February 2, 2017
A. Geoff,
I did the experiments many years ago and the numbers you want are somewhere in my basement in my 100 pounds of notebooks. I did the experiments to show galvanizers how inexpensive flux is in relation to zinc costs.
For 12 degree baumé flux my final formula was flux usage of 1/2 of 1% of zinc usage. Thus for every 100 kg of zinc consumed 0.5 kg of flux was required. This assumes no purification of flux. For a % GZU of 5% this would mean that for every 100 kg of zinc consumed, 2,000 kg of steel would be galvanized.
When I used 71 °C flux and allowed the steel to heat up to the flux temperature (residence time of steel in flux of 3 minutes) twice the amount of flux was on the steel (and more evenly coated with flux) compared to room temperature flux.
Regards,
Dr. Thomas H. Cook
Galvanizing Consultant – Hot Springs, South Dakota, USA
June 27, 2017