400 series stainless steel complex shapes

1. Soak clean for 10 to 30 min

2. Rinse

3. Electroclean at 5 V for 60 to 120 s

4. Rinse

6. Rinse

7. Dip in 20% HCl at 50 °C (120 °F) for 30 s. Alternative: nickel strike

8. Rinse with deionized water

9. Plate to thickness

In Step 1, all alkaline soak cleaners should be operated at their supplier's maximum recommended temperature, typically 60 to 80 °C (140 to 175 °F). Unless otherwise indicated, all other processes are at ambient temperature. In Step 3, electrocleaning is with at least three reversals of current (part, cathodic/anodic, three times) at 3 to 5 A/dm2 (30 to 50 A/ft2). Except for 300 series stainless steel, the final current cycle should be with the part anodic; with 300 series stainless steels, the final current cycle should be with the part cathodic to minimize the formation of an oxide film on its surface.

Activation for Alloy Steels. Before electroless plating, stainless and alloy steel parts must be chemically activated to obtain satisfactory adhesion. For this, a low pH nickel strike is normally used. Two common strike baths are listed below:

Nickel sulfamate strike

Nickel sulfamate

165-325 g/L (22-43 oz/gal)

Nickel (as metal)

35-75 g/L (5-10 oz/gal)

Sulfamic acid (~20 g/L, or 2.7 oz/gal)

to pH 1-1.5

Boric acid

30-34 g/L (4-4.5 oz/gal)

Hydrochloric acid (20° Be)

12 mL/L (1.5 fluid oz/gal)

Temperature

Room temperature

Cathode current density

1-10 A/dm2 (10-100 A/ft2)

Time

30-60 s

Anodes (bagged)

Sulfur depolarized nickel

Operating pH

0.8-1.5

Woods nickel strike

Nickel chloride

240 g/L (32 oz/gal)

Hydrochloric acid

250 mL/L (32 fluid oz/gal)

Temperature

Room temperature

Cathode current density

2-10 A/dm2(20-100 A/ft2)

Time

30-120 s

Anodes

Rolled depolarized nickel

Caution: Insoluble anodes cannot be used. Chlorine gas would be liberated from insoluble anodes.

Caution: Insoluble anodes cannot be used. Chlorine gas would be liberated from insoluble anodes.

Nickel strikes should not be used to cover up improper pretreatment of plain or low-alloy steel. Nickel-strike activation should be considered, however, when processing steel with chromium or nickel contents of over 1.5% carburized or nitrided steels, and stainless steels. Nickel-strike processing should follow acid activation to avoid drag-in of alkaline materials into the strike (Ref 41, 42, 43, 44, 45, 46).

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