Phosphating reduction and waste disposal?

"Phosphating of Metals"
by Werner Rausch

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A. Hi Umesh. I don't know how things are in Sweden, but here in the USA I have watched as the average life of outdoor equipment like patio furniture, barbecue grills, gardening tools, etc., has plummeted from a 10-20 years of useful life, to two or three seasons. This sustainability travesty has occurred because we are focused on the wrong things.

We already know exactly how to properly pretreatment metal but, instead of doing it, we are looking at the pound of phosphate used instead of the tons of steel repeatedly mined, smelted, fabricated, finished, shipped, used for a couple of years and then landfilled ... with the cycle starting over again.

Cars are one of the few things that last, and it's because of proper pretreatment. Proper finishing is key to a sustainable world. Please either accept what I've said or tell me where I'm wrong. Thanks!

Regards,

A. Zinc Phosphate processes that don't use nitrate or nitrites as accelerators will not have any of those components in the sludge. Several other accelerators exist such as chlorate, peroxide, and a few organic ones, all of which have advantages and disadvantages. I'm not up on the Canadian regs, but I know several shops down here that dispose of treated zinc phosphate sludge as a non-hazardous industrial waste.

!! You are stating that several companies dispose of ZINC PHOSPHATE WASTE AS regular trash. That is VERY questionable with the ZINC metal present in the waste and more than likely Nickel if the ZINC PHOSPHATE is used prior to E Coat and particularly if zinc coated metals are being processed.
There will also be TITANIUM from the rinse ahead of the phosphate treatment.

Thanks Peter. A former governor of New Jersey memorably noted: "Toxic is a matter of statute, not opinion" -- which cuts both ways. Things continually change though, and may have changed further in the ten years since the previous postings.

But many regulations are "categorical standards". I know you understand this, but for readers who may be trying to follow along and are less familiar with it, this means that some wastes are categorized by where they come from rather than just their contents. Consumers can throw stuff in the trash or down the drain that would be illegal for many businesses. For example, whereas a homeowner is welcome to flush their toilet waste into a sewer, the rinse water used in a plating shop is regulated and can't go to the sewer without permitting and monitoring even if it's so pure you could serve it in a fine restaurant :-)

So I think it is possible that certain zinc phosphate sludges when used by painters (probably as opposed to plating shops which have different categorical standards) were sent, and could legally go, to a regular landfill. And furthermore, that the rinse water from the process went, and could legally go, to the sanitary sewer.

Is titanium regulated in landfill waste or discharge water? If so, in what categories, or universally? Thanks again.

Regards,

A. Some possible options for handling phosphating sludge:

United States Patent 5273667 (1993) describes a process which involves collecting the phosphate sludge, dewatering using a filtering process, drying the dewatered sludge at an elevated temperature to a moisture content of less than 10 wt.% and reducing the particle size of the dried sludge to less than about 20 mesh. The dried and ground phosphate sludge has been found to be an excellent lubricant additive, which is suitable for use in lubricant formulations designed for the metal treatment, metal forming and industrial lubrication.

The use of phosphating sludge in the process of clinker production is suggested as one of the possible mode of reclamation of such waste by Caponero and Tenorio (Resources, Conservation and Recycling 29 (2000) 169). Their study proves that an addition of up to 7.0% of phosphating sludge to the raw cement meal of Portland cement did not cause any damage to the clinkerization process. Additions of the phosphating sludge up to 5.0% significantly modify only the zinc content of the clinker that was produced. The major element of the sludge, zinc, shows an average of incorporation of 75%.

"Phosphating & Metal Pretreatment"
by D.B. Freeman

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A. Hi Raddagar. Proper phosphating before painting/powder coating typically means the difference between decades of life for steel components (patio furniture, outdoor equipment, barbecue grills, etc.) and a 3-year-minus life. As a student exercise, please consider whether it makes more sense to worry more about phosphating steel items once every 10-20 years or, skip proper phosphating, thus requiring us to mine, smelt, fabricate, paint, ship, and landfill stuff every 3 years?

Phosphating should be an almost non-detectably small blip on the radar screen of people who are truly concerned about the environment and sustainability. While phosphating wastes can and should be treated, should we really be focusing on eliminating the pound of phosphate, or does common sense tell us to start with the tons of steel wasted for lack of proper phosphating before painting/powder coating?

Regards,

? Hi Randy. You didn't mention what kind of business your shop is in, and I think this may affect the answer, as explained in the thread we appended your question to.

Regards,

A. Based upon my understanding of hazardous waste regulations, it is your responsibility to determine if this waste has any hazardous or otherwise regulated contaminants or characteristics. At a minimum you should have an EPA certified lab do a TCLP test, and also analyze for nickel.

Iron and zinc are not hazardous per se, but zinc and nickel may be regulated in your liquid discharge.

Q. Our shop uses the phosphate line to coat 1045 and 4140 steel.

A. I have a feeling that your waste would pass a TCLP. Zinc is not a RCRA waste.

It might qualify as haz waste on the basis of corrosivity - pH under 2 or so. In that case you could fix that by mixing a bit of hydrated lime in it.

Unless, of course, the powers that be decreed this to be an "illegal on-site treatment of hazardous waste."

Jeez Louise.