This procedure describes the start-up of a pickling bath for stainless steel parts. For this set-up a first order of 2000 ltr. pickling bath concentrate has been placed.
Starting up the bath
A bath with a capacity of 4000 litres was used.
The bath was filled as follows:
- 2000 Ltr tap water
- 2000 Ltr pickling bath concentrate
Temperature of the bath:
- After filling up the bath: temperature of 23°C
- After 1 hour: temperature of 20 °C
- After 12 hours: temperature of 17°C
- After 36 hours: temperature of 13°C
Pickling time for stainless steel 304 & 316 is between 60 and 90 minutes at room temperature of approximately 20 °C.
Per 10 °C less, the pickling time will double.
Per 10 °C more, the staining time will be halved.
Therefore, it is important to check the temperature of the bath regularly.
In addition to the improvised pickling bath, a small rinsing bath was also used until the specially ordered rinsing bath was installed. This rinsing bath should undergo a first simple rinse as soon as the parts come out of the pickling bath.
At the start, the rinsing bath, filled with ordinary tap water, has a pH neutral (7) since ordinary tap water is used.
The parts already have a very nice surface after rinsing in the bath. On the weld, however, we can clearly see that black remains. This is iron that came to the surface after pickling and that aggressively adheres to the weld surface.
Rinsing with high pressure
After rinsing in the bath, it is very important to rinse thoroughly with high pressure (min. 150 bar).
There are 2 reasons:
- To fully rinse/neutralise the acidity of the pickling bath.
- To remove all remaining iron from the surface.
