S
PROCEDURE FOR ACID PICKLING
AND PASSIVATION
SPI
1.0
QPP 1000653070010-01
Page 1 of 2
Scope
This procedure is applicable for stainless steel material.
2.0
Definition
Acid Pickling is done for the stainless steel components to prevent them from
rusting.
3.0
Reference
ASTM A380
4.0
Qualification of testing Personnel
Suitably qualified personnel shall undertake Acid Pickling.
5.0
Instructions
Acid Pickling is done for the stainless steel components to prevent them from
rusting. The method followed is explained below:
Standard Reference: ASTM A 380
First of all, chemical cleaning is done to remove all extraneous matter, dirt, dust,
grease, oil, welding slag, loose rust, oxide scales that may be present on the SS
components to avoid the contamination by way of iron pick up.
SEQUENCE OF OPERATION:
Cleaning of segments shall be carried out in the following sequence:
a.
b.
c.
d.
Flushing with the water to remove dirt, dust, loose rust and foreign Matter
Degreasing
Acid cleaning
Final rinsing and drying.
CHEMICALS:
DEN/SF/016/03
1. Caustic potash rayon.
2. Nitric acid.
3. Hydrofluoric acid conforming to ASTM or equivalent. In any case, purity should
not be less than 50% HF by wt.
4. Water/chloride free water (chloride level 50 ppm) should be used for flushing
and rinsing operation.
REV( )/Date
(0)/ 25.08.11
(1) / 03.09.11
Prepared by
MPS
MPS
Approved by
UST
UST
S
PROCEDURE FOR ACID PICKLING
AND PASSIVATION
SPI
QPP 1000653070010-01
Page 2 of 2
PICKLING OPERATION:
1. All the SS castings required pickling should be flushed with water/ chloride
free water (chloride up to 50 PPM) to remove all extraneous matter, dirt and
dust etc.
2. After flushing, degreasing shall be carried out in a Pickling bath to remove
grease, oil and organic coating if any. Degreasing solution shall be Potassium
Hydroxide of concentration 50gm/litre (100% purity basis). Temp. of solution
during pickling shall be 50-55 deg. C for duration of about 1 hr.
3. After degreasing, above segments should be rinsed with above quality of
water. Rinsing should be continued till the neutral PH is obtained.
4. After step 3, above segments shall be pickled with acid mixture of Nitric acid
(HNO3) and Hydrofluoric acid (HF). Composition of pickling solution should
be 10% HNO3 by vol. (on 100%purity basis) and 0.5% HF by vol (on 100%
purity basis). Pickling solution can be prepared at room temperature and for
duration of 15-30 minutes. However exact concentration of acid mixture and
duration shall depend on cleaning of the above segments based on visual
inspection.
5. After pickling, above segments should be rinsed with water.
6. Passivation:
The cleaned segment is then subjected to Passivation process.
The Passivation bath contains HNO3 (20% to 30%) and balance water by
volume. The components are fully dipped in the bath for 30 minutes
(minimum) at room temperature. The components are then cleaned with high
pressure water jet
7. Finally dry all the segments by clean dry air.
PRESERVATION:
DEN/SF/016/03
After the pickling and drying, these segments should be preserved in clean and
dry condition to prevent entry of moisture, dust or dirt.
REV( )/Date
(0)/ 25.08.11
(1) / 03.09.11
Prepared by
MPS
MPS
Approved by
UST
UST
S
DEN/SF/061/04
SPI
PROCEDURE FOR ACID PICKLING
AND PASSIVATION
QPP 1000653070010-01
Page 3 of 2