Pickling and Passivation Procedure

Doc. No.: GASWA/14-10/01

Pickling and Passivation Procedure

Rev.-

00

Date

5/08/2014

AL-GASWA STEEL INDUSTRIES CO. LTD.

PICKLING AND PASSIVATION

TITLE: CLIENT: PROJECT: PO. No

:

KACST STYRENE MONOMER TANK 252829/M/100

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Doc. No. GASWA/14-10/01

Pickling and Passivation Procedure

Rev.-

00

Date

5/08/2014

1. 5/08/2014

00

For Approval

Mubeen Ahmad

M. Ateeq Ashraf

Date

Revision

Description of Revision

Prepared By

Reviewed & Approved By

P

URPOSE The purpose of this procedure is to restore the stainless steel protective thin layer of chromium oxide after welding of Stainless Steel vessels groove (butt) joints.

2. SAFETY PRECAUTIONS To prevent from burns or inhaling the fumes produced by the chemicals during in the pickling & passivation procedure; a) A tool box meeting shall be conducted with all people who will involve in the procedure, explaining them the procedure and measures to be taken during application. b) Work area shall be barricaded and safety signs shall be displaced to keep away the non – concerned people. c) The specified area for the pickling and passivation process will be well ventilated. To avoid unnecessary evaporation, keep the containers closed as much as possible. d) Eating, drinking or smoking in the Pickling area shall be not allowed e) All pickling residues shall be neutralized to protect the environment.

3. PICKLING AND PASSIVATION PROCEDURE 3.1 CLEANING Different chemical and mechanical methods and sometimes a combination of both can be used for cleaning, prior to start the Pickling & Passivation procedure. Followings are the minimum requirements for Pickling procedure. a) All welding flux and weld spatter shall be removed by grinding or blasting. b) All dirt, cinders, fly ash or other extraneous matter shall be removed by brushing with a hard fiber brush (Nylon Brushes) or stainless steel wire brush. Mild steel wire brush shall not be used for cleaning purpose. c) All organic materials, paints, crayon marks, soap, oil or grease shall be removed by washing with any commercial paint remover, (those containing HCl or H2S04 are not permitted) light solvent naphtha dichloro ethane or benzene. Soap solutions or similar detergents may also be used. Motor petrol shall not be used.

3.2 APPLICATION OF PROCEDURE Page 2 of 4

Doc. No. GASWA/14-10/01

Pickling and Passivation Procedure

3.2.1

Rev.-

00

Date

5/08/2014

PICKLING

Pickling is the most common chemical procedure used to remove oxides and iron contamination. Thorough rinsing with clean tap water must follow pickling. The water being used in pickling must have acceptable chloride content less than 50 ppm. Pickling normally involves using an acid mixture containing:   

Nitric acid Hydrofluoric Acid Remainer

3.2.2

: : :

10 – 15% in volume 1 – 5% in volume Water

PICKLING WITH PASTE

The past shall be applied by swabbing on the stainless steel surfaces of a weld joint. The surface shall be exposed to the solution for not more than 30 minutes. During the operation, removal of oxides can be hastened by brushing with a hard fiber or stainless steel wire brush together with clean sand. The pickling agent shall be finally washed off to leave no traces of acids behind.

3.2.3

PASSIVATION AND DECONTAMINATION

The procedure is carried out in a manner similar to pickling but in this case the active agent is Nitric Acid (HNO3). Passivation solution shall be prepared by mixing the following. Nitric acid

:

15 – 30% in Weight

Remainer

:

Water

The weld joints shall be treated with mixture / solution. Allow the mixture / solution 20 – 40 minutes to react with weld joint. After enough time passed, rinse the weld joint thoroughly with clean tap water, preferably using a high pressure water jet containing chloride content not more than 50 ppm. Rubbing or brushing is prohibited during and after passivating.

3.3 INSPECTION The rinsed surface shall be checked with a blue litmus paper. If it turns to red colour, means acid is present there and further rinsing shall be done till satisfactory results achieved.

4. NEUTRALISATION AND WASTE TREATMENT After Pickling & Passivation the waste water becomes acidic and contaminated with heavy metals, mainly iron, chromium and nickel that have been dissolved from the steel. The waste water must therefore undergo neutralization. Waste water can be neutralized using by any alkaline agent.

5. TESTING AND ACCEPTANCE After completing the procedure a thorough inspection of passivatived coil joint shall be carried out. Successful results show the acceptance of Pickling & Passivation procedure.

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Doc. No. GASWA/14-10/01

Pickling and Passivation Procedure

Rev.-

00

Date

5/08/2014

6. DOCUMENTATION Certificate of Compliance shall be prepared by QA/QC Department for successful inspection results.

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