PROCEDURE FOR PICKLING AND PASSIVATION

Work Order NO.

ACC. TO ASTM A 380 Client

EQPT. NO. :- Reference / Specification:

Specification No.:Q 01-F 37 Austenitic and High Alloy Steel Pressure Vessels – Fabrication.

Approved Equipments Inspection & Test Plan Purpose : This practice is applicable to Austenitic Stainless Steel (300 series) parts/assemblies for removing metallic contamination and welding and heat-treating scales.

Precleaning : Prior to pickling, clean the stainless steel surfaces and remove all extraneous matter with a stainless steel wire brush or hard fibre brush. All organic material shall be removed with any paint remover like light solvent naptha or benzene or equivalent. Motor Petrol shall not be used.

Pickling Solution: Aqueous pickling solution shall be as follows :Nitric Acid (Tech. Grade) 15 to 25% plus Hydrofluoric Acid 1 to 8%.Temperature : 21-60°C, for 5 To 30 minutes.

Pickling Procedure:

(1) Ensure the part/item is in its simplest possible geometry before subsequent fabrication or installation steps create internal crevices or undrainable spaces that may trap pickling agents.

(2) Ensure the surface to be pickled is thoroughly cleaned and free from shop soil, oil, grease and other contaminants.

(3) When size and shape of the product permit, pickling shall be done by total immersion in pickling solution.

(4) When immersion is impracticable, pickling shall be done by:(a) Wetting the surface by swabbing with pickling solution or by spraying the pickling solution on

the surfaces of the product.(b) Partially filling the item with pickling solution and rotating or rocking to slosh the solution, so

that all surfaces receive the required chemical treatment.(c) Circulating pickling solution through the item for sufficient time till complete descaling is

ensured (If rocking or rotating is impracticable.)

(5) The surfaces should be kept in contact for about 15 to 30 minutes or till complete descaling is ensured.

(6) Over pickling shall be avoided. Continuous exposure to pickling solution for more than 30 minutes is not recommended.

(7) In order to hasten the removal of pickling smut (scale particles and products of chemical reaction), intermittent scrubbing with a stainless steel brush or fibre bristle brush, in conjunction with pickling or the initial rinsing, may be carried out.

(8) To minimize staining, surfaces must not be permitted to dry between successive steps of the pickling & rinsing operation.

PP/07-026/001 2 of 2 0 27.07.2007Document No. Page Rev. Date Prepared by Approved by

Form No. : 02 – 07 0 19.10.99 Engineer (QA & C) Head (QA & C)

PROCEDURE FOR PICKLING AND PASSIVATION

Work Order NO.

ACC. TO ASTM A 380 Client

(9) After pickling, the surfaces shall be rinsed with enough water till no trace is left behind on the surfaces.

(10)The surfaces shall be thoroughly dried.

Passivation: (1) Clean the surfaces by scrubbing water and detergent (such as, Trisodium Phosphate, TSP) using fibre

brushes.

(2) Rinse the surfaces with water to remove residual chemicals.

(3) For further cleaning and passivation, treat the surfaces with Nitric Acid solution (20-50%) at temperature 50-70°C, for 10-30 minutes.

(4) Rinse the surfaces thoroughly with water.

(5) Dry the surfaces thoroughly.

(6) Protect the passivated surfaces from further contamination.

PP/07-026/001 2 of 2 0 27.07.2007Document No. Page Rev. Date Prepared by Approved by

Form No. : 02 – 07 0 19.10.99 Engineer (QA & C) Head (QA & C)