Letter 29046

Some important queries about hard chrome plating [India] 

May  ++++

Respected Sir,

A project work is being carried out in HAL,Bangalore complex in aircraft division.The project focuses on components that are hard chrome plated to thickness 150-200 microns which go for grinding and later for assembly.Some of the questions which is of importance are:
1. How to clean/filter the chromic acid and sulphuric acid solution for hard chrome plating?
2. How to calculate the efficiency of the hard chrome plating bath? please provide the formula.
3. How to improve the efficiency of the bath, if it is less than 10-12%?
4. How to clean (mechanically/chemically) the lead-antimony anodes in hard chrome plating bath?Please mention the frequency of cleaning.
5. In a given tank(based on volume), how to decide the number of components to be loaded at a time in the bath? What are the limiting factors?
6. Can we combine load the parts at a time of different size and shape?
7. Some agitation is observed near the cathode during hard chrome plating.  is it necessary to use mechanical/air agitation during the plating process?
8. After hard chrome plating and de-embrittlement it is followed by grinding.Can you suggest optimum grinding equipments or parameters to avoid cracks during grinding?

I would be thankful to you if you can answer my above queries as soon as possible.

Thanking you,          

SEEMA.S.
student - BANGALORE, KARNATAKA, INDIA

You certainly have a practical student project there, Seema. Your questions sure beat asking whether Taco Bell sauce or Pepsi cleans pennies best! On the other hand, though, you are asking for free, wholesale, in-depth, vertical technology transfer while offering not even a thimbleful of knowledge and findings in return. So please frame your questions in terms of what you already know about the topics. For example:

1. The chrome plating solution can be filtered, using conventional approaches, but with plastics that are resistant to attack. PVDF (polyvinylidene fluoride) components are available from companies like George Fischer. Have you tried filtration; what were the results; what specific problems did you encounter? If you have not tried filtration, what are the indications that make you think you should; what holds you back in your particular situation?

2. The efficiency of a plating bath is obtained by dividing the actual amount of metal deposited by the amount that should be deposited according to Faraday's Law. What efficiency have you been obtaining?

3. The efficiency depends on a number of factors including the temperature and concentration of the plating bath and how close the workpieces are positioned to the anodes. Please describe these parameters for your installation. The efficiency also depends on what catalyst is used. You apparently are using conventional sulphuric acid presently. Have you tried fluoride catalysts? If so, why did you revert; if not, why not? Have you tried the proprietary etch-free catalysts like HEEF-25 that offer up to 25 percent efficiency?

Thanks in advance for your replies!

Regards,

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

Dear Seema

Nice project for a student.

As Mr. Mooney suggested Heef 25 can be a good answer of all your questions. Also you want to read some plating engineering handbook. All your questions have very simple answers but you do need the skills of a professional plater to accomplish them all. Hey, good luck.

Hemant Kumar
- Florida, USA

Dear Seema,
Your questions are already answered by Mr.Mooney and Mr.Hemant.Regarding cleaning of the anodes,you can not clean the anodes while they are inside the plating bath.You need to remove it and dry them and use metallic brushes to clean .The number of components which can be plated per load depends on area to be plated and capacity of the rectifier connected to the tank.
All the best,

Jaikrishnan.C
- Bangalore, India

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