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Nickel plate, blistering when chromed

Dear sir Ted, greetings,I have problems chroming over watts nickel. substrate is steel and aluminum.it seems that whenever I plate chrome over nickel the nickel blisters and peel off along with the chrome. I observed proper pretreatments, I buff the nickel to shine before I chrome it for 3 to 4 minutes, 1 amp/sq.inch. I have a 2 phase rectifier. I also wonder if it is possible that my rectifier is contributing to the problem. thanks in advance.

Chris Sian
student - Bacolod City, Philippines
May 14, 2008

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May 15, 2008

Based on the small amount of information given, the chrome has a high internal stress, which is pulling the nickel under plate off of the parent metal because it has poor adhesion to the metal.

Your steel either has not been cleaned adequately, or is not properly activated.

On aluminum, you have to use a zincate before the nickel, and then it helps to use a proprietary alkaline electroless nickel as a strike before the regular nickel.

Polished nickel is not easy to get clean and activate, so I would have thought that the chrome was separating from the nickel.

James Watts
- Navarre, Florida

Sir Watts, thank you for the information, though your answer is limited it helped a lot. my other problem is the misplating of chrome, 2min. of chroming plating seems short and cannot cover entirely. I really need your suggestion thanks

Chris Sian
- Philippines
May 27, 2008

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May 27, 2008 Hi Chris, I did hard chrome plating, so my approach would be different than yours in that I used 2 to 4 minutes to bring the voltage up to final voltage, so the part (heavy) could warm up to tank temp. It all depends on how much chrome you need to put on, anode to cathode distance, temperature and voltage (amperage per square inch). Two Minutes would only put on the most minimal flash of chrome and that would be on the high current density areas of the part (sharp corners/edges). 4 amps per square inch will plate about 0.001" per side in about an hour. Each minute of plating should give you about 0.000,016" of chrome (16 millionths of an inch per min) I actually got more plate than that per hour, but I was using a proprietary chrome solution with conforming anodes and anode /cathode spacing of about 1/2 an inch. James Watts - Navarre, Florida hi , James is correct , it sounds like you havnt cleaned the substrate prior to plating . also , have I miss read your letter - does the part your plating consist of both steel and aluminium ? or have you got 2 different parts ? If , as I read your letter , your part consists of aluminium and steel , your part will be very difficult to plate as both materials need different pre-treatments. As for the poor coverage of the chrome plate , it depends on the shape of the part . it is very difficult to "throw" into corners and around holes, etc... chrome has poor throw efficency , so a strike will be needed before setting the desired current. Jay Smith - Essex, UK May 28, 2008

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dear sirs,
thank you for your helpful responses, your information was right, I started using HCl 30% concentrate, some steel doesn't react as fast as others so I leave it submerged for an hour until it darkens. then I dip it in deionized h20. then I dip it in watts nickel for an hour.( since I haven't made up a bright nickel solution yet). talking about bright nickel I tried saccharin and Thiourea [on eBay or Amazon] mixed with watts nickel and in very high temperatures, around 60 °C the nickel plate seems to turn real bright but peels off by hand. but anyways I am still researching on how to make bright nickel and if you have any information that you can share, that would be a big help. this is a great site I have learned a lot from experts like you. Thank you and I am very grateful for your help.

Chris Sian
- Philippines
June 30, 2008

A. Chris,
Clean your part in a caustic solution first, then rinse well then into the acid for about 5 minutes. 1 hour is mega too long and causes other problems.
Sacharin will brighten and harden nickel, but it takes an extremely tiny amount and then it causes such a huge internal stress that the nickel will actually flake off.

James Watts
- Navarre, Florida
July 1, 2008