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topic 50922

Platinised titanium anodes for hard chrome plating?

Hard Chrome  
Plating pointer 

       

A discussion started in 2001 but continuing through 2018

(2001)

Q. What causes low efficiency in chrome plating? What can be done to improve it? If plating is done with platinized titanium how to maintain condition of anodes?

Payal Mag
- Charlotte, North Carolina


(2001)

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 for 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
Anders Sundman
3rd Generation in Plating
Consultant - Arvika, Sweden



Electrodeposition of Chromium from Chromic Acid Solutions
George Dubpernell

(2001)

Q. Dear Mr. Sundman,

I understand that if we clean platinized titanium the chromate layer developed will get spoiled and expensive anodes may get spoiled. Do you suggest to rinse them? Should one clean them with a soft brush? Do you suggest chrome solution in touch with anode even when we are not plating? How much lead oxide do you recommend in bath when platinized titanium is used?

Payal Mag [returning]
- Charlotte, North Carolina


(2001)

A. Payal,

Try to clean them in NaOH 100 gr /l and Rochelle salt 100 gr /l and 100 liter water. Use a larger lead anode than the rack, that is enough. When you not use the solution you can electrolyse by using a small cathode bar and a larger anode area.

Regards

anders sundman
Anders Sundman, 4th Generation Surface Engineering
    Sundman & Nylander AB
Arvika, Sweden




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(2001)

Q. We are looking for a information on use of Platinum Clad Anode for Hard Chrome Plating operation. Can it be used in Hard Chrome Plating operation in place of conventional Lead Tin / Antimony Lead Anode?

R. K. Khare
- Mumbai, Maharashtra, India


(2001)

Hard Chromium Plating
by Guffie
from Abe Books

or

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


(2001)

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


(2002)

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 coating limits the use. The whole anode immersed inclusive the splash zone needs to be covered with the MMOA-layer.

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


(2004)

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



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Chromium Plating
by Weiner & Walmsley
from Abe Books

or

(2003)

Q. We use the standard 40 mm dia, 8% tin lead anodes for hard chrome plating. The problem that is frequently encountered is that there are chromium trees on the edges of large objects and the center of the object (usually flat) has less thickness of chrome. We were advised to use platinized titanium anodes as they can be shaped as per the cathode size and they also permit smaller inter-electrode distances to prevent large edge buildups. We plate flat object of size 3 ft x 5 ft and use currents up to 6000 Amps. Can anybody explain how platinized titanium anodes are used? Can they replace the tin lead anodes?

Nitin Kibe
technical director - Pune, Maharashtra, India


(2003)

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
Anders Sundman, 4th Generation Surface Engineering
    Sundman & Nylander AB
Arvika, Sweden




(2006)

Q. I have a problem that the trivalent chromium amount rises.
We use platinised titanium basket anodes and lead rods
What can I do about the problem?
How can I reduce amount of trivalent chromium?

Fikret MUTLU
- Turkey


June 6, 2013

A. Fikret, you can reduce trivalent in hard chrome by using a porous pot.

Zaim Frluckaj
- Los Angeles, California, USA



To minimize searching and offer multiple viewpoints, we've combined multiple threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



January 9, 2009

Q. We are using Tin-lead anodes for hard chrome plating. the anodes are 40 mm dia. x 1200 mm long. Anodes are hung in a straight line to plate on rectangular sheets. I want to know if we can use Platinised Ti anodes for this job. If anyone has used such anodes, what are the advantages of it. I understand that initial cost is the biggest disadvantage. But do they offer good economies in running? Do we have to use Lead anodes also along with it?

Nitin Kibe [returning]
engineer - Pune, India


January 27, 2009

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


February 19, 2009

Q. Dear sir,

What is the average life of platinized titanium mesh anode (2.5 micron) in fluoridefree Cr+6 bath if plant is running 24 hrs/365 days?

We use lead-tin anode at present.

Can we use Iridium oxide coating anode in replace of Pt anode in same bath if this is advantageous with regard to cost/life?

regards,

Anil Sharma
employee - Nagpur, India



February 24, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Chrome Plating for rotogravure cylinders? I have a question on anodes for the chrome plating process. Currently we are using nickel/lead anodes in chromic acid for plating. Wastage in the current process is high and we end up continuously replacing the anodes.

Can we use titanium anode bars as a replacement for these nickel/lead anodes ... ?

Regards,
David

David Ignatius
- Tamil Nadu, India


February 27, 2012

Q. Experts -

I have seen numerous responses on the anode for plating.

What do you think is the best anode that can be used in the hard chrome plating process? We would like to come to the most cost effective metal.

David Jose
- India


February 28, 2012

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



April 9, 2018 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Anodes of tin/antimony are good for chrome plating or platinized titanium anodes?

Haroon Akmal
- Lahore Pakistan


April 2018

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,

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



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