Where the
world gathers for metal finishing
Q&As since 1989


-----

Plating on Stainless help

1998

Dear Helper,

We are doing small plating shop especially in gold plating. We are production company but also received recondition plating work.

Until now we got no problem in plating various metal except plating on stainless steel. We have tried some formula from several books, but until now was no satisfaction. We got problem of peeling after bubble present especially on the moisture contact area. Is that call the hydrogen embrittlement? We have tried to bake immediately after plating, but the happened come again.

Our procedure :

1. Soaking in 30 gr/lt NaOH + 30 gr/lt sodium carbonate / washing soda [affil links] for 1-2 mnt. Wash.

2. acid dip 5 % H₂SO₄. Wash.

3. Activating Cathodically in 250 ml/ltr H2SO4^^HCl, 5 A/ft€, 5 mnt.

4. Direct without washing to 0.4 g/ltr copper sulphate [on eBay or Amazon]strike 750 ml/ltr H₂SO₄. 50 A/ft€ for 3 mnt. (We tried woods nickel strike, but it seem copper strike is better).Wash 2x.

** Direct go to step 7 or next:

5. Cyanide copper plating to 2 micron thickness (optional). Wash.

6. Bright watts Nickel Plating.Wash.

7. Acid Gold Strike (citric acid base). Wash

8. Cyanide Gold Plating until 10 micron. Wash.

9. Immediately bake 300 °C for 2 hour.

The finish seem good and bonding well, but after 1 month bubble start come out at the moisture contact area.

Please help, Your advice is greatly appreciate.

Anton Bijosono
Ujung Pandang - Indonesia

---

Wood's nickel strike should be used in step 4.

  
Tom Pullizzi
Falls Township, Pennsylvania
1998

Definitely a Wood's strike, rinse rapidly but well and move with all due haste to the next plating tank. It takes very little time to passivate in air, especially if allowed to dry even a tiny bit. Works great. Use the lower limit of nickel and the middle limit of HCl and do not use sulfur depolarized nickel and carbon treat about once a month.

James Watts
- Navarre, Florida
1998

---

Thanks Tom & James,

I wrote a bit mistake about step 4, It should 0.4 gr/ltr CuSO4 + 750 ml/ltr HCl ( not H2SO4).

As I wrote, I tried use the wood's strike and the bubble still come. I wonder something wrong with my procedure.

Frankly, I didn't use deionized water for rinse. Is this the source of problem ?

Can you tell me if this problem is caused by Hydrogen Embrittlement or porosity ? The bubble & delay peeling only come out at the moisture contact area.

Anton Bijosono
Ujung Pandang - Indonesia
1998

---

I do not know what you mean by "moisture contact area". Is this an area of the finished part which is immersed in water or a chemical in the field?

  
Tom Pullizzi
Falls Township, Pennsylvania
--

 

---

Hydrogen embrittlement causes a weakening of the metal, normally along grain boundaries. Bubbles or blistering is caused by the part not being clean enough or active enough. You have not said what kind of SS it is. Very high nickel or very corrosion resistant SS like 316 or 321 may require a more aggressive etch.

If your part is a poor casting, you may be trapping gas in the pores and it is slowly causing the bubbles. A better surface finish may help. Grit blasting with Aluminum Oxide grit may improve the surface enough as well as give you an active surface to start with.

James Watts
- Navarre, Florida
1998

Thank's Tom.. The finish parts are Watch case, and the problem happened at the side that contact with skin.

Anton Bijosono
Ujung Pandang - Indonesia
1998

---

1998

Hi,

Tom and Jim are right, step # 4 has to be a nickel strike. It is imperative.

You also need an electrocleaner. As you already have cyanide in your premises , a cyanide electrocleaner should be used. Make it up with sodium cyanide, sodium hydroxide and carbonate. Two electrocleaners, one cathodic and one anodic electrocleaners will be perfect.

I also noticed that you have no wetters in your soak. Try to add some.

Step # 3 and the copper plating can be omitted.

By the way, when do you notice the peeling, right after plating, after a thermal shock test or after usage?

Sara Michaeli
Tel-Aviv-Yafo, Israel

---

Hi, Anton. Let me make the score 4 to 0 that you must switch to Wood's nickel strike :-)

Please see Jack Dini's "Electrodeposition" for proper operating procedure and adhesion test results. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 9, 2009