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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
May ++++
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
June 16, 2007
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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