Metal finishing Q&As since 1989
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Plating chrome over chrome
Q. I was after some feedback on how to plate hard chrome plating over existing chrome in a HEEF 25 type solution. We have tried a few different ways and none seem to be giving us consistent enough results to keep persisting with them. The plate seems to cover about 90% of the job beautifully but a few small areas blister or flake. We know of other people who consistently obtain perfect results. Our suppliers seem to know very little about the product in terms of procedures that need to be followed to obtain good results.
I would greatly appreciate any suggestion.
Regards,
John AdamsPlating shop - Melbourne, Victoria, Australia
2004
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A. Mr. Adams, One of my clients is plating hard chrome over hard chrome in HEEF 25 type of process whenever he doesn't get required thickness in an automated line. If you are not stripping chrome Please follow the steps below. 1. Give good pretreatment prior treatment. 2. Pass low current for about 15 minutes i.e around 25 % of the total current you generally pass. 3. After the above step plate the substrate to the required thickness, but pass around 20 % less current density than your regular current density and give more time. The above steps should help you in getting good plating as my client is already getting. N.K.Praveen Kumar- Secunderabad, India 2004 A. You probably need to go to tech services at the manufacturer for the best information. You need to be careful with the caustic clean and the acid etch as it is easy to mess up the surface. We used to use a short reverse in the plating tank followed by a voltage ramp up to the final voltage/amperage. If the part has any considerable size, are you letting it come to temp before starting. What temp are you using? Tank anode or conforming? James Watts- Navarre, Florida 2004 2004 A. I don't have anything specific to HEEF, but this should work: 1. Soak clean to remove any grease, oil, etc. Rinse. 2. Reverse current in chrome 1 to 2 minutes about 6 volts. 3. Direct current starting at zero volts, then ramp up to full plating current over about 5 minutes.  Jeffrey Holmes, CEF Spartanburg, South Carolina |
A. John. You cannot do the etching in HEEF 25 solution, but if you have a regular hard chrome plating solution you can do the etching in that solution. Etch for two minutes, don't rinse the area when you move the part from the tank to tank. Let the part take the solution temperature with no current, raise the current to 0,5 A / dm2 for 5 minutes, raise the current once again to 2,5 A/dm2 for 5 minutes. Look at bubbles in the chrome solution they will be a little bigger than when you chrome with right current. Raise the current very slow to the plating current. All activation steps: read Mr Watts suggestion.
Regards
Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2004
Thank you to everyone for your responses. I have gotten in contact with tech advisors in U.S and they have faxed me appropriate information very similar to the responses posted. I greatly appreciate your time and efforts to make response. So far the jobs we have tried are working out well. Thanking you again.
Plating shop - Melbourne, Victoria, Australia
2004
Q. Sir,
If chrome plated parts are undersize in grinding then is it possible to replate chrome instead of deplating & then plating?
- India
June 27, 2013
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A. If the company that you are doing this work for will allow it, THEN it is a possibility. - Navarre, Florida July 5, 2013 July 7, 2013
- Maharashtra, Kolhapur, India |
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Ed. note: Hi Dhanajay. Please use the search engine to find "adhesion test chrome", and post any followup questions on one of those threads. Thanks.
Q. Recently we machined chrome plated shaft ID beyond allowable limits. Can anyone advise me how to chrome plate over chrome without any failure.
Regards
G G
- ABU DHABI HARARE
October 7, 2015
A. Sir
It is possible to plate Hard Chrome over Hsrc Chrome provided the initial coating is more than 100 microns. The job to be plated must be polished using fine abrasive media around 320G-400G then followed by normal pretreatment process and Reverse etching in the plating tank for about 2-3 minutes at around 1-1.5 amps/inch square.
Start plating at 2 V; gradually raise in Voltage of 2 amps every 4-5 minutes until the required current density is attained. Please be sure all anodes are working, and gassing is observed on all these anode while reverse etching. Good luck.
mahendra gargattiGargatti Electroulocs - BELGAUM.KARNATAKA INDIA
January 24, 2016
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Ed. note: Sorry, we don't know what "Hsrc" means or whether it is a typo.
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