Titration Application Note H-143

Sulfuric acid and tartaric acid in

tartaric sulfuric anodizing bath
Rapid, sequential determination using a thermometric
sensor (thermometric titration)

Tartaric Sulfuric Anodizing (TSA) is an established technique for corrosion

protection in the aerospace industry. It is an alternative to the environmentally
harmful chromic anodizing process. As such, a method to monitor the levels of
sulfuric acid and tartaric acid in TSA plating baths is required. Potentiometric
titration methods have been developed, and are widely used across the industry.
Their disadvantage is that two titrations with different electrodes and solvents are
required.
In this Application Note, an alternative method is presented, where the
concentration of both acids is determined in sequence using a thermometric
sensor. Compared to potentiometric titration, thermometric titration is faster and
more convenient (no sensor maintenance required). On a fully automated system,
the determination of both parameters takes about 7 minutes.
 Method description

Sample Analysis of samples

Tartaric sulfuric anodizing bath 2 mL sample is pipetted into the titration vessel. 40 mL
deionized water is added using the pumps. The solution
is then titrated with c(BaCl2) = 1 mol/L until after the
Sample preparation exothermic end point to determine sulfuric acid content.
To the titrated solution 5 mL β(KF) = 300 g/L is added and
No sample preparation is necessary. the solution is titrated with c(NaOH) = 2 mol/L until after
the exothermic end point to determine the total acid
content. The tartaric acid content is calculated by
Configuration subtracting the sulfuric acid content from the total acid
content.
859 Titrotherm 2.859.0010
814 USB Sample Processor (1T/1P) 2.814.0010 After the titration the solution is aspirated and the sensor
and buret tips are automatically rinsed with deionized
772 Pump Unit – aspirate 2.772.0120 water.
800 Dosino, 3x 2.800.0010
802 Stirrer 2.802.0020
Parameters
Dosing unit 10 mL, 2x 6.3032.210
Titration Sulfuric acid Total acid
Dosing unit ETFE 5 mL 6.1575.150
Mode TET TET
Sample rack 22 x 120 mL 6.2041.470
Start volume 0 mL 0 mL
Stirring propeller (intensive) 6.1909.060
Pause 20 s 20 s
Titration head for 859 Titrotherm 6.9914.159
with 120 mL PP beakers Stirrer -15 -15
Sample beaker 120 mL 6.1459.300 Dosing rate 2 mL/min 2 mL/min
Thermoprobe HF 6.9011.040 Filter factor 50 70
Damping until 0.3 mL 0.3 mL
Solutions Stop volume 7 mL 7 mL

Titrant 1 c(BaCl2) = 1 mol/L Evaluation start 0.3 mL 0.3 mL

Barium chloride 244.28 g BaCl2 is weighed Reaction type Exothermic Exothermic
into a 1000 mL volumetric EP criterion -30 -60
flask and dissolved in
deionized water. The flask is
then filled up to the mark Result
with deionized water.
Sample no. Sulfuric acid / Tartaric acid /
Titrant 2 c(NaOH) = 2 mol/L (n = 5) (g/L) (g/L)
Sodium hydroxide 80 g NaOH is weighed into a
1000 mL volumetric flask and Bath 1 42.9 ± 0.6 78.2 ± 0.7
dissolved in deionized water. Bath 2 44.5 ± 0.7 81.0 ± 1.0
The flask is then filled up to Bath 3 43.9 ± 0.8 81.0 ± 1.7
the mark with deionized
water.
Potassium fluoride β(KF) = 300 g/L
300 g KF is weighed into a
1000 mL volumetric flask and
dissolved in deionized water.
The flask is then filled up to
Version 1, published in February 2019

the mark with deionized

Titration Application Note H-143

water.

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