The following is condensed from a paper given at the Aerospace/Airline
Plating Forum in Tulsa, OK.
Lean & Green Manufacturing
Lean and Green manufacturing involves
many factors. One of the most important factors is reducing the
volumes and costs of chemicals used in the production process. Industry
uses acids for surface activation (electroplating applications),
stripping (electroplating and metal finishing) and pickling to remove
iron oxide mill scale (galvanizing, steel/wire). When these acids
become contaminated, the acids are treated on-site or hauled off-site
for disposal. This is at a substantial cost to industry.
The late Dr. John Wagner devoted his
professional career to the study of inorganic catalyzed reagent
chemistries. His discoveries have found applications in the wood
preservation industry, certain site remediation projects and in
the purification of organic and inorganic acids. The focus of this
paper is the application of this proprietary catalyzed reagent for
the purification of acids in the metal finishing industries.
The catalyzed reagent is a proprietary
blend of soluble silicates, which allows for the effective immobilization
of soluble metals by reacting with them to form insoluble metal
silicates and insoluble oxides. Soluble silicates are a unique class
of polymeric compounds in which sodium oxide (Na2O) is associated
with silicon dioxide (Si O2) generally in ranges varying from 1:1
to 1:3.22. These depolymerize in dilute solutions to form chains
of silica and oxygen. With negative charges on some oxygen, reaction
occurs with metal ions having positive charges to form stable, insoluble
metal silicates and oxides..
Gwen Wagner began marketing the chemistry
in 1999. The first commercial application was at Amplate in Charlotte,
NC. Over a period of 9 months, the chemistry was added to all acid
baths. None of these acid baths have ever required waste treatment.
The next use of the chemistry at Amplate
was the application to acid and alkali rinse waters. With pH adjustment
to 7.6 and appropriate filtration, Amplate was able to go to zero
discharge on these rinses. The chemistry was later applied to zinc
rinses, which also resulted in zero discharge. Chromate rinse waters
containing Cr+3 and Cr+6 were also segregated and treated with the
chemistry with mixed results. Amplate discontinued the use of their
ion exchange and electrocoagulation systems and replaced them with
the reagent chemistry and standard filtration.
The chemistry is currently being used
in approximately 150 electroplating plants, 3 anodizing plants,
1 wire plant, 2 galvanizing plants and 1 steel pickling plant. The
following data is typical.
1. Canadian Electro Galvanizing plant rack line:
This plant uses 40% HCl in a 350-gallon
tank to remove mill scale and to activate the metal surface for
their pipefittings. This plant dumped the bath weekly when the iron
concentration reached 4%. The plant has been using the catalyzed
reagent chemistry and has not dumped the bath in 14 months. The
average iron concentration has stabilized at 2.8% Fe. A Flo-King
filter is used to remove the iron precipitate and the filter is
cleaned daily. Cost savings of $9,654 CND have been verified and
these savings do not include reduced downtime and reduced amounts
of F006 filter cake generated.
2. Illinois Electroplating Plant rack Zn line: - DuQuoin
This plant previously used 30-50%
HCl for surface activation and dumped 55 gallons per day of the
partially spent acid to waste treatment. The addition of the chemistry
was made in early 2004 and no acid dumps have occurred. In addition,
the plant has reduced the bath concentration to 20-30%, while maintaining
required quality control. Acid consumption has been reduced by 50%
with similar reductions in caustic neutralization costs and hazardous
waste generation. Acid makeup is 12 gallons a day and 1 quart a
day of catalyzed reagent is used.
3. Connecticut Electroplating Plant barrel Zn lines: - Thomaston
This plant has used the chemistry
since March 1, 2003 in a 220 gal 30% HCl bath and a 10% H2SO4 bath.
The HCl bath was previously dumped two to three times a week and
the H2SO4 was dumped daily. The baths have not been dumped in 12
months. Since the chemistry removes iron in the acid tanks, iron
contamination in the zinc-plating tank is reduced. Previously, the
zinc bath was treated with HMnO4 three times a week and is now treated
once every two weeks. The HCl tank is filtered with one 20
cartridge, 10-micron filter that is changed weekly.
4. North Carolina Electroplating Plant Aberdeen
This plant uses HCl for pickling and
activation of carbon steels and stainless steels and or stripping
of zinc coatings from various base metals. Plant processes include
stainless steel black oxide, ferrous metal black oxide, zinc phosphate,
iron phosphate and manganese phosphate heat-chemical coatings.
The plant has utilized the chemistry
since October 2001 and the two HCl tanks have not been dumped since
that date. Plant records indicate:
95% reduction in F006 hazardous waste/ Reduced HCl usage/ Reduced
Reduced plating system downtime for maintenance/Reduced wastewater
Reduced rinse water contaminants
A simple pH neutralization system
is currently being installed to close loop the acid & alkaline
rinses. This will be the subject of a future paper.
5. Georgia Electroplating Plant - Valdosta
This client has a 500 gallon 40% V/V
HCl tank used to strip chrome from steel, stainless steel, aluminum
and yellow metals. Previously, stripping times were erratic due
to dissolved metal concentrations and oily film on the acid tank.
The chemistry has eliminated the oil
in the strip tank and stripping time has decreased due to consistent
acid bath quality, purity and strength. This plant has been using
the chemistry since 2003; and the acid baths have not been dumped
and copper immersion plating has not occurred.
6. George Plating Shop - Toccoa
This plant plates large quantities
of yellow metals, which causes copper to build up in the HCl and
H2SO4 tanks. Both acids were used at 20% V/V concentrations and
the HCl tank was dumped 3 times a year and the H2SO4 tank 4 times
a year due to copper immersion plating problems.
7. Indiana Electroplating Plant Fort Wayne
This company does semi-bright/bright
nickel and trivalent chrome plating. The 1,000 gallon 20% HCl tank
was previously dumped monthly and has not been dumped in that last
12 months. The plant manager estimated acid and caustic savings
of over $6,000 a year. The filtration consists of five 20
30-micron cartridges that are changed once a week. The generation
of F006 hazardous waste has been reduced.
8. Canadian Hot Dip Galvanizing Co.
This galvanizing company began using
the chemistry on a 3,000 gallon 20% HCl pickling tank in May 2003.
Prior to using the precipitation chemistry, the iron concentration
would increase to 6% Fe within 3 months. The cost to dispose of
this bath was $5,000 CND or $20,000 CND per year.
Using the catalyzed reagent, the reagent
cost to make the initial 1% charge on the 3,000 gal tank is $2,430
for 30 gallons of reagent. On an annual basis, this tank will consume
approximately 3,350 gallons of 32% HCl, which requires 33.6 gallons
of reagent. The total first year reagent cost is $5,150 as compared
to a disposal cost of $20,000. Second year reagent costs are projected
at $2,720 a year, which would give an 86.4% savings. The operating
cost for filters and the amortized cost for the filtration system
are not included in these savings.
Over the last ten months, the iron
concentration has gradually increased and stabilized at 7% Fe. Because
the acid is clear and free of organics, the customer reports superior
pickling results at this higher Fe concentration. String would cartridges
were originally used and later changed to poly spun cartridges,
as this reduced the iron concentrations by 2%. A 15 cartridge 20-micron
filter is used with weekly cartridge changes.
The customer also reports another
important benefit. The amount of iron drag out into the flux tank
has been reduced, which reduces the solids formation in the flux
tank. This has reduced the maintenance time to clean the flux and
has contributed to more consistent quality control of the galvanized
This facility has approximately 98,000
gallons of pickle acid in the plant. By using the savings demonstrated
on the 3,000-gallon tank, projected annual savings could approach
$480,000 a year.
9. North Carolina Captive Shop Charlotte
This plant uses 40% nitric acid and
10% ammonium bifloride in one 500-gallon etching tank and 15% citric
acid in the 500-gallon passivation tank. Dumping frequency would
vary from 2 to 3 times a year. The acids are used in the stainless
steel passivation line. When the acid was new, passivation time
was 20 minutes but would lengthen to 120 minutes before dumping
The acid purification chemistry is
now being used and passivation times remain constant at 20 minutes.
The same quantity of work is now being passivated in 446 hours as
compared to the previous 1,560 hours for a reduction of 70% in production
Savings in acid and caustic consumption
are calculated at $8,300 a year with additional savings in waste
treatment, operator time, reduced F006 amounts, and reduced utility
consumption in the wastewater treatment plant.
10. Tennessee Rack and Barrel Operation Memphis
This company began using the chemistry
in June 2003 in one 1,000 gal HCl tank. Later, the chemistry was
added to another 1,000 HCl tank, a 3,000 gal HCl tank, and a 750
gal HNO3 tank. None of these tanks have been decanted or dumped
in over 9 months.
Over a 6-month period of using the
chemistry, caustic consumption dropped 46.3%, HCl consumption dropped
70.8% and hazardous waste generation dropped 34%.
The following table gives actual savings:
6 Months Data
20o Be HCl
The NET savings do not include:
Reduced operating costs on sludge drier. Better plating due to
better acid quality control.
No production downtime due to dumping. No acid dumps to batch treat
Improved activation due to lower metal concentrations. Lower TDS
to the POTW.
Summary and Conclusion
The catalyzed reagent has been used
commercially for over 3 years in over 150 plant locations. Economic
and environmental benefits have been substantiated by plant operating
personnel and these benefits can include the following:
Elimination of Acid Dumps/Eliminate On-Site Neutralization of Off-Site
Increased Pickling or Surface Activation Rates/ Reduced Fuming from
Hot or Ambient Acid Baths
Reduced Contaminants in Rinse Waters/ Reduces Environmental Liabilities
Elimination of Production Downtime Due to Tank Dumps/ Lowers Acid
Minimal Capital Investment Filtration only/ Reduces Dissolved
Solids to Wastewater Treatment
Possible Change to Smaller Quantity Generator Status/Helps Attain
Near Zero Discharge
Reduces TSS and TDS Loadings to UF&RO Polishing Systems/ Removal