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


-----

Trouble in zinc plating already electroless nickel plated of low carbon steel casting valve

The part will accept the Electroless Nickel process, but will not accept a charge in order for the Zinc Plate to be applied. There looks to be excessive sand inclusion and rough spots after machining and nickel plated. Our Plating vendor suggested it might also have something to do with the Impregnate process? Any suggestions.

Alaa Odeh
Manufacturing of Industrial fuel controls - Rockford, Illinois, USA
2006

---

Has your plating vendor tried ACID zinc plating? Cyanide processes will not deposit on cast substrates because of a hydrogen overvoltage issue.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

Thank you for the response. I am checking on the Acid Zinc Plate process with the supplier. would impregnation of the casting prevent zinc from adhering. the supplier is claiming that impregnation will effect the zinc plating process. thanks

Alaa
- Rockford, Illinois, USA
2006

---

Anything is possible, Alaa, but impregnation is supposed to improve the plating not interfere with it. But first things first; there is really no point to pushing on until you determine whether your plater is trying to plate cast iron from a cyanide bath. Let us know.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

---

Yes the impregnation does interfere, and generally the cleaning processes further affect the plate-ability on impregnated metals. I'm unable to understand the reason for the change of spec; if you want zinc you might still need to flash EN plate before zinc plating.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2006

---

I received a response on the Zinc plating technique. They use a Non-CN Alkaline base. The problem seem to show up at the Zinc charge op. The supplier indicated that "somewhat Large Black" substance is coming out of the casting at the electroclean "reverse current" op, possibly impregnation material or sand. What is interesting is that the casting is getting uniform electroless nickel film of about .0006", perhaps because EN does not require a charge?. at the Zinc charge patchy type non continuous bare spots are appearing? Any suggestions? do you think acid zinc plating is better for this low carbon casting steel? if so do you know of any good suppliers in Co or Illinois? thanks for the help

Alaa Odeh
- Rockford, Illinois, USA
2006

---

I'm quite sure that acid zinc would be a lot better than alkaline zinc for these particular parts, but I will defer to my very knowledgable colleague KV, that it may not be good enough. You may still need to EN flash. Yet, I think it's worth a try!

The free service that you are availing yourself of is made possible by our supporting advertisers, and we would be mistreating them if we spent their money posting recommendations and testimonials about other shops abilities with acid zinc or electroless nickel. So please visit our Jobshops page. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

---

Dear Alaa;

Mr Ted Mooney was dead on target with getting you to look at the process in the first place; Alkaline zinc generates much more hydrogen at the cathode surface and hence is still much worse than the Cyanide Process in plate-ability of cast, sintered, powdered, metal injection moulded metals.

Acid zinc will easily plate over your impregnated material and its what you need to do in the first place; but the reason I recommended continuing with Electroless Nickel is to counter with post plating bleed out issues, it looks like you are already causing the bleed out on account of using alkaline zinc.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2006