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PICKLING ACID BATH: IRON CONTROL USING
THE KLEINGARN CURVE
Alana Fossa, AGA
Galvaforum 2021
INTRODUCTION
▹Kleingarn Curve
▹Cost Benefits
▹Ongoing AGA Research
▹AGA Pickling Bath Maintenance Calculator
HYDROCHLORIC (HCL) IRON MAINTENANCE CALCULATOR
▹HCl pickling baths become ineffective at certain combinations of iron and acid concentrations
▹Without a recycling unit, iron concentration in the pickle bath is controlled with manual additions of water and acid to extend life
▹Calculator is based on the Kleingarn Curve
THE KLEINGARN CURVE FOR HYDROCHLORIC ACID BATH
▹Tells you when the iron concentration of the bath results in:▹50% slower pickling rate
▹Optimal pickling rate
▹Or saturation (pickling not possible)
▹Charts are based on hydrochloric [HCl] acid concentration in g/L at 21°C
▹Impact of Zinc% not considered
WHAT ABOUT THE SULFURIC ACID BATH?
▹Today there is no Kleingarn Curve for sulfuric acid▹Research performed in Germany
where hydrochloric acid is used
▹New AGA Research Program (2020-2021):▹Develop Kleingarn Curve for Sulfuric
baths
▹Study impact of Zinc concentration (%)▹hydrochloric pickling rates
▹sulfuric pickling rates
COST SAVINGS AT THE PLANT
▹Reduced acid use
▹Acid disposals are less frequent▹In one 20-week study, a galvanizer
found disposal frequency at his galvanizing plant increased from every 6 weeks to every 9.5 weeks.
▹Reduced transportation and disposal cost
EXAMPLE: ADDING 12 M3 (12,000 L) FRESH ACID
▹Pickle Bath Properties:▹33 m3 (45.3 t) pickling
solution
▹4% HCl (hydrochloric acid)
▹13.2% Fe (iron)
▹1.37 Specific Gravity at 20 °C
EXAMPLE: ADDING 12 M3 (12,000 L) FRESH WATER
▹Pickle Bath Properties:▹33 m3 (45.3 t) pickling
solution
▹4% HCl (hydrochloric acid)
▹13.2% Fe (iron)
▹1.37 Specific Gravity at 20 °C
AGA IRON MAINTENANCE CALCULATOR
▹The calculator provides:1. Location of your pickling bath
on the Kleingarn Curve right now
2. Volume acid and/or water to add
3. Volume for disposal
4. Location of your pickling bath on the Kleingarn Curve after acid and/or water additions
Initial Input Needed
Use Guess & Check method. Adjust until you get desired result on chart
New Pickle Bath and Rinse Bath Properties after acid/water additions
Adjust until you achieve desired result on chart
Adjust until you achieve desired result on chart
GUIDANCE FOR HCL PICKLE BATH ADJUSTMENTS
1. If Acid Low & Iron High ▹add concentrated acid
▹adjust by adding water/rinse water
▹Formula to estimate volume (Liters) acid:
𝑉𝑖𝑛𝑖𝑡𝑖𝑎𝑙(𝑚3) × %𝐻𝐶𝑙𝑑𝑒𝑠𝑖𝑟𝑒𝑑 −%𝐻𝐶𝑙𝑖𝑛𝑖𝑡𝑖𝑎𝑙
%𝐻𝐶𝑙𝑓𝑟𝑒𝑠ℎ 𝑎𝑐𝑖𝑑 −%𝐻𝐶𝑙𝑖𝑛𝑖𝑡𝑖𝑎𝑙
GUIDANCE FOR HCL PICKLE BATH ADJUSTMENTS
2. If Acid & Iron Low:▹add acid and continue pickling until pickle times improve
3. If Acid & Iron High:▹add rinse water and/or fresh water
4. If Acid High & Iron Low:▹add rinse water and/or other spent acid and continue pickling
SUMMARY
▹Kleingarn Curve improves calculations for acid and water additions▹Reduced acid use
▹Less frequent acid disposal
▹Cost savings at the galvanizing plant
▹AGA Pickling Bath Maintenance Calculator (see AGA website)▹Sulfuric acid calculations
QUESTIONS & COMMENTS
▹American Galvanizers Association▹www.galvanizeit.org
▹Contact Information ▹Alana Fossa
▹Sr. Corrosion Engineer
▹720.361.4485
