6. Corrosion caused by hydrobromic acid
NPB may hydrolyze to produce hydrobromic acid, just like chlorinated
solvents hydrolyze to hydrochloric acid. The corrosiveness
of hydrobromic acid and hydrochloric acid to carbon steel
(CS) and stainless steel (SS) are compared under different
conditions. The tests show hydrobromic acid has lower corrosiveness
than hydrochloric acid. See below for details.
Table 5. Comparison
of corrosiveness of HCl and HBr, mil per year
| Temperature, °C |
Substrate
material |
37% HCl |
48% HBr |
0.1N HCl |
0.1N HBr |
| 25 |
1010CS |
5650 |
368 |
83 |
40 |
| 25 |
316SS |
2150 |
3 |
0.05 |
0.03 |
| 53 |
1010CS |
|
|
417 |
63 |
| 53 |
316SS |
|
|
none |
none |
7. Hydrolysis
Hydrolysis stability of NPB preparation and
1,1,1-trichloroethane are tested by the following procedures.
1. Mix 100ml of test solvents with 25ml of water, reflux for
164 hrs.
2. Immerse SS316 into the resulting solution.
3. Add 10g of granular charcoal into the solution, reflux
in a Soxhlet condenser.
After completion of the test, the organic
phase and water phase are analyzed respectively, as show in
the table below. The hydrolysis of NPB preparation
is 2-3 times faster than 1,1,1-trichloroethane. The result
is still acceptable regarding the signifacantly weaker corrosiveness
of hydrobromic acid compared with hydrochloric acid.
Table 6. Comparison of hydrolysis of NPB preparation (A) and
1,1,1trichloroethane.
| |
Procedure I |
Procedure II |
Procedure III |
| A |
B |
A |
B |
A |
B |
| SS316 |
none |
none |
corrosion observed |
corrosion observed |
corrosion observed |
corrosion observed |
| CS |
none |
none |
none |
none |
none |
none |
| Water phase
|
| Color |
none |
none |
green |
green |
green |
green |
| Acidity, % |
3.33 |
1.39 |
2.13 |
1.43 |
3.89 |
1.50 |
| Halide, % |
3.03 |
1.05 |
2.47 |
1.12 |
3.96 |
1.27 |
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