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topic 4846

Blistering Problem on Zinc Die Casting


I am running a watch case plating factory and just start to add a zinc die casting plating line, however, blistering problem occasionally occur. It may happen in different lots or certain percentage within a lot.

I am understand that the blister may due to the process of (1) the pre-cleaning, (2) the electro-cleaning, (3) acid dip, (4) cyanide copper plating, or (5) the quality of the die casting.

Can anyone advice a good process to plate a zinc die casting product in order to prevent the occurrence of blister?

Is it help if the cyanide zinc plating is plating to the zinc die casting before cyanide copper plating ?

If it is due to the poor quality or low density of zinc die casting itself, Is there any process for a plater to mininize the blister in plating

Deville Yiu
- Hong Kong, China


Yes, it is all of those things and more. You will need some help on the ground. I would start with adding proprietary vendors of plating chemicals, and then get technical help from the people who sell you chemicals.

tom pullizzi monitor
Tom Pullizzi
Falls Township,


Dear Mr Deville Yiu, Your question reminds me of the story of a visitor to the Boeing factory who asked a simple question 'How do you make airplanes?' Whilst Mr. Pullizzi has rightly pointed you in the direction of the Chemical Vendor, I would also advise you to get hold of a person with considerable hands on experience in plating Zinc diecastings to establish your line. I don't think that Zinc plating would help much.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind supporting advertiser
Bangalore, Karnataka, India

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Dear all!

I'm a student & going under industrial training in a filter manufacturing company. I've been assigned to work in plating area. From last few weeks blistering/swelling of plating is observed on the caps( not on all the caps). I've studied there process but unable to find the root cause. Can anyone advice me on this problem & can suggest the ways to remove it. Copper wires are used to hang the caps during plating but after plating when wire is removed it leaves the impression.The cap outer dia. is 88.8 mm & inner 56 mm.Are there any more ways other then barrel plating. I'm not a professional but still I hope you people can help me out.


Archana Mishra
- Punjab, India


You didn't say what the caps are made of (I assume steel or diecast zinc), nor what you are plating them with, nor where on the caps the blistering occurs, nor if it occurs between plating layers. So there is really little to say except that blistering occurs when there is no adhesion or very poor adhesion, and there should be excellent adhesion. Rack marks are part of the plating process; but it sounds like you should be using plating racks rather than individually jigging the caps with wire.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

July 24, 2011

hello dear Devill yiu and archana

plating on zinc base die casting is not easy compared to other metals, and main two reasons of blistering on zinc base die cast components:
1- process blister :-this type blister is created during die casting process
2-service blister :- this type blister is created during plating service (delay blister :-after plating 1 day, 2 day or same day but it is service blister.

secondly electroplating process is not cheap. it is electrochemistry but now without blistering plating on zinc base die casting is possible but need some care like
1- proper zinc alloy composition
2- proper die casting process (melting temp./pressure /cooling time /releasing agent spray /etc.
3- suitable buffing polishing compound
4- buffing wheel and system and pressure during buffing work
5- suitable buffing compound remover
6- location of storage after buffing
7- do not touch open hands after buffing (need hand gloves)
8- after buffing the product is not stored a long time, maximum 24 hours. if possible do plating before 24 hours
9- proper metal cleaner
10- soak time and temp very important
11- ultrasonic cleaning
12- electrocleaning cathodic proper cd
13- activate suitable fluoride base
14- high speed cyanide base cu (important bath condition /temp./cd and choose right anode OFHC cu (oxygen free high conductivity)
15- acid cu plating (important bath condition and temp. chilling need,
16- nickel plating (important bath condition and operating
17- all rinsing steps are very important and carefully need.zinc is very sensitive metal and rinsing /cleaning steps/water break test is very important in plating process
18- if possible please use all steps use dm water
19- if possible all plating tank use with filter
20- use good company rectifier (minimum repels )
21- use hot air blower after plating
22-any problem after plating do you investigation need
check step by step first to last plating where problem and what problem (blister / pealing /pitting / etc.

Kanjibhai Patel
- Rajkot Gujarat India

July 26, 2013

Q. If there are pinholes on zinc die casting material, how can they be covered from nickel electroplating?

Deepak Rathod
- Rajkot, Gujarat, India

July 26, 2013

A. Hi Deepak. They can't. Sorry, but very high quality castings -- free of porosity and coldshuts -- are essential for successful plating. There is no way around it


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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