Summary for flux for galvanizing cable tray Discussion
Flux for galvanizing cable tray items is discussed alongside the full pretreatment and kettle setup. The questioner, a new galvanizing company in Saudi Arabia, asked for the best flux, Baumé range, and kettle temperature to achieve 65–80 micron coatings on cable trays and ladders, and outlined a process using acid degreaser, 20% HCl, rinses, flux, galvanizing at 455 °C, and quench. Dr. Thomas H. Cook warned that lowering the zinc level by 300 mm would likely burn out the kettle at the wash line within about six months, said 10% acid degreaser is unusually strong, and noted that 10% HCl is too concentrated and will create excessive fume and corrosion. He also said 455 °C is hotter than usual and suggested about 835 °F instead, while asking about zinc chemistry and kettle details. Mohamed Saad added that for cable trays the degreaser is especially important because of heavy oils, and advised checking supplier control points and considering the ferrous content in the pickling bath to allow lower HCl concentration.
October 26, 2011
Q. Dear sir
We are a new galvanizing company in Saudi arabia. Basically we manufacture cable tray and ladders, miscellaneous items. We need to galvanize the same for 65 micron to 80 microns.
Can you please suggest us the best flux , its baumé to be maintained and temperature in the kettle at which we can achieve the same .
Our bath size is as follows
7 mt long x 1.3 mt wide x 3 mtr deep
We have reduced the height of zinc level by 300 mm , so the dept of the zinc level in the kettle is now 2.7 mtr
We intend to follow following sequence:
Acid degreaser (10%)- HCL acid 20% -water rinse X 2 – flux (double salt? pls suggest) — Galvanizing bath (temp 455 °C please suggest) — quench
Kindly guide at the earliest.
Dharampal Salooja
Plant Manager Galvanizing – Jeddah, Kingdom of Saudi Arabia
October 26, 2011
A. Sir:
By lowering your zinc level by 300 mm (11.8 inches) you will certainly burn out your kettle within about 6 months at the zinc/air interface (wash line), because the insulation from the top rim down (on the outside of the kettle is likely only 6 inches vertically downward).
An acid degreaser is almost never used at a high concentration of 10%. Most acid degreasers are based on phosphoric acid and are quite expensive. I prefer caustic.
HCl at 10% is too concentrated and will cause much fume and corrosion in the plant. HCl requires some iron (Fe+2) to pickle properly, so at first pickling will be slow.
455 C is 851 F and is certainly on the hot side these days. A more usual temperature for zinc is about 835 °F.
What will be the chemistry of your zinc? (e.g. any additives like aluminum, etc.)
From what country did you get your kettle, and kettle furnace?
I enjoyed my time in your city some years ago.
Regards,
Dr. Thomas H. Cook
Galvanizing Consultant – Hot Springs, South Dakota, USA
A. For the acid degreaser, please contact the supplier to know the control points; I think that for cable trays your most important bath is the degreaser tank due to the huge amount of oils at its surface; this oil protects the surface against corrosion (low conc. acid will do the job)
At Saudi Arabia the temp. of acid usually above 30 °C, so please consider the ferrous content at the pickling bath, it will let you make good pickling with lower Hydrochloric acid concentration.
Mohamed Saad
– Jeddah, Saudi Arabia
November 27, 2011