Platinised titanium anodes for chrome plating

A. Hi Payal.
Low efficiency in a chrome solution occurs when you have bad anodes (if the anode is yellow you must clean or change the anodes), low ratio or wrong catalyst. If you use platinized titanium anodes the trivalent chrome will be high in your solution and that decreases efficiency in the solution. This type of anode will not oxidize trivalent chrome to hexavalent chrome. You can try to use a little small cathode rack (count this in your calculation for the area) besides your part when you use platinized titanium anodes and bigger lead anodes to get the trivalent chrome to oxidized to hexavalent chrome.
Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

A. Payal,
Try to clean them in NaOH 100 gr /l and Rochelle salt [on eBay or Amazon] 100 gr /l and 100 liter water. Use a larger lead anode than the rack, that is enough. When not using the solution you can electrolyze by using a small cathode bar and a larger anode area.
Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

A. Dear Mr. Khare,
Platinised Titanium can be definitely used for Hard chrome plating. Only disadvantage is that it very expensive and it does not convert trivalent chrome back to hexavalent chrome. The chrome chemistry should also not contain any Fluoride.
GS sharma
- Mumbai, India

A. The problem of Trivalent can be solved by keeping some lead in solution. Say addition of lead carbonate in bath can create a film on platinized titanium which can keep bath in balance. The ratio of anode and cathode will also play role in maintaining balance. The life of platinized titanium anode is very long.
Payal Mag
- Charlotte, North Carolina

A. Anodes for Chrome Plating in Fluoride Containing Baths Fluorides are added to Cr⁺⁶ and Cr⁺³ baths. Sodium fluoride up to 500 mg F^-/ l is added to activate steels by polarity reversal. Fluoroborates or silicofluorides are added in self-regulating Cr⁺⁶ baths. The F^- content varies with the bath producer and reaches up to 2 g F^-/l.

Only the free F^- attacks the metals. The severeness of the corrosion depends on the F^- content, other bath parameters and the anodic current density and starts from the weakest surface areas, like scratches, fissures and pores in a coating. The user seldom knows the F^- content of his bath. Therefore tests are advised for the producers or users of chrome baths.
Unplatinised Ti, Nb or desired other noble metals are submerged into the chrome bath under working conditions, contacted anodically. While increasing the voltage the tested metal shows with the jerky current increase it's breakdown-voltage.

Practical experience shows: Ti withstand F^- up to 10 mg / l, a PTA with 5 microns Pt works nearly one year at 50 mg F^-/ l, nevertheless we recommend for this use a PNA. Nb withstands a F--content until 600 mg / l, a PNA is used from 50 to 500 mg F^-/ l up to currents of 20 Amps / sq dm. For even higher F^- contents PTW can be used. But metal mesh out of tungsten cannot be produced.

Also fluoride is added to decorative black Cr³⁺ baths. For these baths mixed oxides activated titanium (MMOA) is applied. In the version of IrTa-oxide users have added F^- up to 50-100 g F^-/ l. The coating withstands up to 600 g F^-/ l, but scratches and pores in the PTA with 5 microns Pt-layer failed after 11 months in a bath of 90 mg F^-/l. MMOA Ti-anodes were used for years in a trivalent chrome bath at 70 mg F^-/l.

Conclusions: PTA can only be used at low F^- content of ~ 10 mg F^-/l. For F^- content up to 600 mg/l PNA is be used, higher F^- content requires tungsten as the base. The user is advised to test the suitability of Nb or W as anode substrates under the actual plating conditions.
K.S. Selva
Sai Electro- - Chennai, India
2002

A. Platinised Niobium anode is the best solution for Hard chrome plating bath. If you have high fluoride in the bath platinised titanium will not stand.
Vanajambika Jeyakumar
- Chennai, India
2004

A. Nitin,
Yes you can use platinized titanium anodes. Or use a platinized thread. When using platinized anodes in a chrome solution the building of trivalent chrome will be very fast. Because platinized anodes can't oxidize the trivalent to hexavalent chrome. You can eliminate this by using a lead anodes besides and a small rack on the cathode beside the part and there make the oxidize of trivalent chrome to hexavalent.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

A. Fikret, you can reduce trivalent in hard chrome by using a porous pot.
Zaim Frluckaj
- Los Angeles, California, USA
June 6, 2013

A. Jay,
There is no definitive answer to your question. The longevity depends on what type of bath the anodes are used in, current density used, anode to cathode ratio, total plating Sq', and the efficiency of the bath. With good plating conditions, I've only had to replace platinized anodes once every three years in a hard acid gold bath. The bath was used daily, but with moderate use.
Mark Baker
Process Engineer - Syracuse, New York

A. Hello,
Well, platinized titanium having the advantage not to develop such high amount of lead sludge which will, according to local governmental laws, have high discharge costs caused of the toxicity. Also titanium platinized anodes are non-corrosive in presence of fluoride. Disadvantage is, that the platinized titanium anodes are not really good in oxidation of trivalent chrome to hexavalent chrome, so either way, you will need to keep a few led-anodes or you have to have external an device which will oxidize trivalent to hexavalent. Also, the platinized titanium anodes having a limited life time (consumption of plating during process) and which will mean approx. 2.5 micron plated will be held for 1,000,000 A-hr approx.
Regards
Dominik Michalek
- Mexico City, Mexico

A. Hi Anil. Dominik answered that: in his opinion/experience, approx. 1 million amp-hours.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. That would require a complete chapter of a book, not a paragraph or two from an unknown person on a web site. You probably need to hire a knowledgeable consultant or be prepared to do a lot of literature searches.
James Watts
- Navarre, Florida

Hi, Siva. James has given you the route to an authoritative answer. But we've merged your inquiry into a thread which discusses the subject at very good length :-)
Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Dear,
The life of Tin Lead is limited. You need to clean and replace Tin lead often. Platinized Titanium gives uniform thickness. Of course you can't use just Platinized Titanium anode. Some keep small tin lead also in bath to maintain lead oxide or you have to add lead oxide initially. The only disadvantage is higher initial cost for Platinized Titanium anodes. Take care of not spoiling platinum coating. Don't use steel brush to clean it.
Kaushik Magiawala
- Ahmedabad, India

A. It's not. Good luck.
Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. The burning is from a very high current density area at the lip of your tube. The solution to this is having the anode shorter, so that it is further away from the lip. A quick fix would be to wrap about 1/2 an inch on each end of the anode with platers tape. This might require a dab of maskant on the tape edge to keep it from starting to unwind.
Since you are not burning except on the edge, I would not reduce the anode diameter since titanium is a poor conductor of electricity. Do some calculations to see if you can safely do it. If you can, it probably would make racking a bit easier.
James Watts
- Navarre, Florida

A. It is pretty much whatever works for you. We bought bulk lead, silver and tin using about 6% tin and 1% silver. We recycled our lead mats on a rather regular basis and added to the pot as required. Notice that this is a (mesh) mat and not a stick anode.
We bought scrap tire balance weights and added by experience to get the antimony that hardens the lead. It does not take much.
James Watts
- Navarre, Florida

A. Hi Haroon. We added your question to a topic which already discusses it. You can use lead-antimony anodes unless using a mixed catalyst (fluoride) bath; in that case lead-tin should be used for longer life. You can use platinized titanium unless using a mixed catalyst (fluoride) bath in which cases other substrates like niobium are suggested on this page. Good luck.
Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Fred. Can you please introduce yourself and your situation so we don't have to -- probably incorrectly -- read between the lines?
I have personally never heard of silver as an anode material for chrome plating, and it's not mentioned in any of my three books about chrome plating; I suspect (but don't know) that it would de-plate. Further, the lead is required to re-oxidize trivalent chrome unless you are thinking of an auxiliary anode and you have additional lead anodes at work in the tank. What type of catalyst are you using, Sergeant, fluoride, or HEEF (MSA)? This might affect whether silver plating could be used.
Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Parmod. That question was already answered so we appended your inquiry to the discussion rather than starting a new thread. Basically, there are advantages to platinized titanium, but it has the disadvantage that harmful trivalent chrome quickly builds up -- and using some lead anodes addresses the problem.

Good luck,
Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey