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Galvanising Ash Generation Benchmarking

November 26, 2008

I would like to know which are the best figures for Zn ash generation expressed as grs/ sq. m..
And, which are the best practices to keep these figures the lowest?

Thanks in advance and regards,

Arturo Blanco
- Monterrey, Mexico

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November 28, 2008

You should be more specific in your question - or define it better.
Ash production in what type of galvanizing? Continuous strip or jobbing hot dip?
Per square metre of what? zinc surface area? Of steel dipped? Of shop floorspace?

Different types of galvanizing use different methods of measuring ash production.
For example some jobbing hot dip galvanizers measure in kg ash produced per tonne of steel galvanized, some in kg per tonne of zinc consumed.

And the rate of production is very dependent on the type of material being coated, and the fluxing system in use.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

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Sir:

For a "dry" kettle the usual ash generation is about 0.8% of production for no ash box, 0.4% of production for a manual ash box, and 0.2% of production for a motorized ash box. This would be for a weighted average steel thickness of about 0.17 inches. "MZR" zinc/ash recovery machines usually yield about 0.2% of production for ash.

Causes of excessive ash include: bad flux, sinking skimmers, excessive skimming, too much or too little aluminum in the zinc, poorly pickled steel, excessive oil on the product, etc.

What do you have now for ash production based on galvanized product and what is the weighted average steel thickness?

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA
December 1, 2008

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Dr. Thomas H. Cook
Thank you very much for your kind answer

Geoff:
Thanks for your answer, and I am sorry I didn't specify the product / method: it's hot dipping steel pipe.
Regards,

Arturo Blanco
- Monterrey, NL Mexico
December 6, 2008

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Typical ash production for jobbing hot dip galvanizng is about 0.5 to 0.8% expressed as weight of ash divided by weight of steel galvanized.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

December 8, 2008