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topic 13098

Stannate (Tin) Plating Process


 

Q. What is a stannate process? I think it is also know as a 10-step process involving Tin and Cyanide. Who in the U.S. uses this process?

Thanks,

Brandon Hellenbrand
- Fairburn, Georgia, USA


 

A. Hi, Brandon
The chemical symbol for tin is Sn. Practically, 'stannate' just means alkaline tin electroplating as opposed to acid tin plating (sometimes called stannous sulfate). There might be cyanide somewhere in the overall plating cycle, or in older versions of the stannate process but there need not be. Good luck.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


 

A. Let's read about the stannate process:

The Immersion Deposition Process, D.S. Lashmore, Aluminum Finishing Seminar,Vol II, St. Louis, MO, 30 Mar - 1 April, 1982, Aluminum Association, Washington, DC. and Pretreatment for Plating on Aluminum Using The Stannate Process, Jongkind and Seyb, ibid.

Related stuff for tin plating:
Control of Anodes in Alkaline Tin Plating, M&T Chemicals, Rahway, NJ, Technical Data.

Anode maintenance in the Alkaline Stannate Tin Plating Bath,
Lowenheim, Metal & Thermit Corp. New York, NY., reprinted from March 1951 issue of Metal Finishing.

Technical Bulletin, M&T Chemicals, Rahway, NJ, Alkaline Tin Plating with M&T Stannates

tom pullizzi portrait
Tom Pullizzi
Falls Township, Pennsylvania


 

A. The stannate process is not going to make your aluminum adhesion problems go away.

Todd Osmolski
- Charlotte, North Carolina, USA


Stannate process is too slow

2007

Q. Does anyone have a process for speeding up the potassium stannate process using Tin and Potassium Hydroxide?

Mark McCaughey
Metals & Additives - Indianapolis, Indiana, USA


2007

A. Hi, Mark. I presumed the original inquiry was about a stannate plating process (alkaline tin electroplating) but the responses (from Tom regarding Lashmore's paper, and from Todd regarding adhesion) lead me to believe it might instead be about an alternative to zincate for preparing aluminum for electroplating (such as Atotech's Alstan process) -- but it's still not clear to me.

So now I have to ask which topic your stannate inquiry is about? :-)

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



Missing book pages about filming the anodes

2007

Q. I've purchased the fourth edition of Electroplating Engineering Handbook and wouldn't you know, the exact page I need was misprinted with a different page. The publisher will not help me out. Can anyone summarize plating bath tables 25 and 26 for Tin (pages 256, 257)? Is there any mention of brighteners for Alkaline Tin (sodium Acetate?), and the purpose of "Filming" the anodes?

Larry Smith
Plating Engineer - Tucson, Arizona, USA


2007

A. We sent you the missing pages, Larry. The acetate is mentioned, as is the necessity for filming the anodes -- but not why or how. That is covered in full detail though in the Garden State Branch AESF Electroplating Course Manual" in the "Tin Plating" chapter by F.A. Lowenheim. In brief, the anodes will dissolve as Sn+2 instead of Sn+4 if the anodes are not 'filmed' at high current density. Quoting Lowenheim:

"The only critical factor in operating stannate tin baths is the proper control of the anodes. With proper anode control, operation is easy and trouble-free; without proper anode control, good results cannot be obtained".

Good luck.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



Need Alkaline Tin Plating Process Chemistry

March 26, 2009

RFQ: Hi I am looking for supplier who can supply us the following chemical Alk Tin Plating with Stannates ( mix with Potassium Hydroxide)

We want to plate on Carbon steel material. product OCTG oilfield Coupling
Type of Plating ID plating and Thickness about 64 to 104 micron.

We used to buy the chemical in Singapore. Presently there is no company selling in Singapore

Please kindly advise us where we can buy.

Kris Mano
plating shop - Singapore
outdated



Volts low/Amps High in Stannate Tin Plating

September 22, 2010

Q. Hello,

I am manufacture of brass casting and do tin plating for for corrosion protection. We have been having problems with the tin anodes not holding the film. We film the anodes initially with a surge of 8-10 Volts and this starts the film, but shortly there after we will lose the film. We also have notice the amps are rather high 150 amps with the volt at 4-5. The solution is 10oz gal on the Stannate tin and the Sodium Hydroxide is 1.2 oz per gal. The anode to cathode is 2 to 1. What could cause the amps to increase with the volts so low?

Thanks
mike

Mike Hrevus
Manufacturer - St. Louis


September 24, 2010

A. You probably need to reduce the number of anodes to increase the anode current density and voltage. That should be all that is needed.

If that is not sufficient to get a good gold colored film, you may need to reduce the sodium hydroxide concentration a little with acetic acid.

Lyle Kirman
consultant - Cleveland, Ohio


Filtration for alkaline tin plating bath

Tin and Tin-alloy Plating
from Abe Books

or

November 4, 2010

Q. We have a problem with sludge build up in our alkaline tin plating process and are considering a continuous filtering process to remove it. If we do will this:
1) Improve the quality of the plate?
2) Decrease the plating time?
3) Reduce the amount of tin used?

Also an answer as to "why" on all 3 questions would be most appreciated.

Larry Correll
carbon brush manufacture - Greenville, South Carolina


October 2013

A. Hi Larry. In his rather exhaustive coverage of Alkaline Tin Plating in the aforementioned "Garden State Branch AESF Electroplating Course Manual", Lowenheim never even mentions filtration. It is not necessary, but whether it should be employed is probably a matter of your Philosophy of Quality ... some shops feel filtration should be employed on all process tanks, and D.I. water used everywhere, and that failing to use these measures is old fashioned and loose. So, in answer to your questions --
1). Yes, it can improve the "quality of the plate" by insuring no particles are occluded.
2). No
3). No.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



Is stannate the answer to zincate adhesion issues?

November 11, 2010

Q. I am drawn back to Todd Osmolski's comments. Here's my situation.
I used the double zincate system to plate Mid P EN then finish off with rhodium plating on 2024 Al alloy. I have adhesion problem (about 10 %).
I've been told that replacing the first zincate step with an acidic tin immersion coating may help improve the adhesion problem. Or is adhesion problem on alloy 2024 just 'the nature of the beast'.

SK Cheah
- Penang, Malaysia


November 11, 2010

A. If you add an alkaline nickel strike, at near room temperature and then go into the regular EN, I predict that your rejects will drop to a very low number (near zero) The ammonia smell is about the only drawback and the results are fantastic. With one short rinse, the slightly alkaline film of water helps to kick off the EN.
Note, if you do not have a heavy use of the strike, consider adding cooling or you will plate out on the tank during idle periods. It is quite active at temperatures around 75 °F.

James Watts
- Navarre, Florida


November 16, 2010

Q. Thank you, James. Many commentators of this site are proponents of an alkaline EN strike. Does your statement hold true even if the regular EN is maintained at 1~3 MTO for zincated 2024 ?

SK Cheah
- Penang, Malaysia


November 16, 2010

A. It certainly does. A big reason is that the alkaline EN strike does not eat off any (very little) of the surface of the zincate as the acid EN will do quite rapidly. 1-3 MTO's on EN is very expensive. The strike should allow you to go to 3-6 MTOs If you can load the EN tank to at least the minimum recommended surface area to be plated. Also, try to always have stuff in the tank as soon as it gets to temperature. Try to get the temperature down as soon as possible after the last part comes out. Cooling is great if you have it. I always saved my last water make-up for when the last part came out of the tank. Bad memory remembers it lowering the temp by 5 - 10F. Lowering the temp by 10F as soon as the last part comes out will probably get you an additional MTO as well as the nitric acid tank stripping is a lot easier.

James Watts
- Navarre, Florida


November 17, 2010

thumbs up signJames, thank you very much. That's a whole load of valuable information.

SK Cheah
- Penang, Malaysia


Alkaline Tin Plate Build-Up Problems

September 19, 2013

Q. I have recently been trying to achieve an alkaline tin deposit at multiple mils thickness (1-2) that is uniform and will clean up to a bright, smooth finish when polished, per customer requirements.

The issues that are being encountered are that the deposit it is either too rough, and will yield a frosty appearance when polished in certain areas, or too pitted, and they will not polish out. We have been able to minimize the problems by plating at low CD, but it is still present to a degree.

We have done some testing with a new solution which shows that the nice finish is do-able, but not with our present bath. And even if we were to make up a new solution to process this work, we do not know what is causing the failure, and will not be able to prevent recurrence of the problem down the road.

So my question would be, are there known contaminants or tank controls which may cause what we are seeing? And are there any recommendations for how to control them?

Thanks!

Andrew Lambers
Process Engineer - Dayton, Ohio, USA


September 26, 2013

A. Stannate plating baths are great for thin deposits, like 0.2-0.4 mils, but tend to become rougher and treed on thick deposits. To plate 1-2 mils and get a smooth deposit, you may have much better luck with an acid tin plating bath.

Lyle Kirman
consultant - Cleveland, Ohio


What is "Plating Grade" Sodium Stannate?

December 22, 2017

Q. What is the difference in Sodium Stannate Grades? I am working to a Boeing spec (BAC5717) and it states "Sodium Stannate - Plating grade or better".

Bob Foster
engineering - Chicago, Illinois


January 17, 2018

A. Hi Bob,

Plating grade Sodium Stannate usually refers to Sn assay ≥42% with all impurities (Pb, Sb, As, Fe, NO3, free alkali, etc.) sum up together ≤3% by wt.

Regards,
David

David Shiu
David Shiu
- Singapore



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