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A tape titled "The Lost Art of Tin Nickel Plating" by L. Morin, dated 1990 was received by finishing.com, inc. from the author, Lou Morin in 2001. Notes were taken on the contents of the tape for the purpose of a study of this electroplating process. It is hoped that the information in this study, along with publication of podcasts of portions of the audio tape, will be useful to professional metal finishers who wish to add this alloy to their repertoire.
The information presented in the Morin tape, in the opinion of this writer, does indeed show differences between the experiences of Mr. Morin and the data presented in the literature. The reader should listen to the tapes and make their own judgement on how to use the information for their own use. Mr. Morin describes a simple control of his tin nickel formulation with only tin and nickel analysis, Hull Cell control of grain refiner, and one additive control for pH adjustment.
Lou Morin, 1990, audio tape "The Lost Art of Tin-Nickel Plating" finishing.com library, Brick, NJ
Electroplating, J.B. Mohler, Chemical Publishing Co., New York, 1969
Metal Finishing Guidebook and Directory (MFGD), 2002 Guidebook and Directory, Tin-Nickel Alloy Plating, S.K. Jolata,
Ibid, Test Methods of Electroplating Solutions
finishing.com gives no warranty, express or implied, on the accuracy of any information contained in this informational bulletin. The chemicals and procedures described in this document are hazardous and users of this information must verify any and all of it before using or testing in their own facility. The information is for review and use only by professionals trained and experienced in the art and science of commercial electroplating. The hazards associated with tin-nickel alloy electroplating require special techniques, experience, plant, and chemicals which need special treatment. The environmental, waste treatment, safety engineering, and plating of this alloy to commercial applications can only be done successfully in a quality controlled electroplating plant by experienced chemists and engineers.
No part of this bulletin should be considered complete as a guide to successful tin nickel alloy plating. The information is only a starting guide for those who wish to embark upon a process of learning, understanding, and research into the safe and efficient use of nickel alloy plating.
No chemical or device described in this informational bulletin should ever be purchased, stored, or used except in the confines of a secure commercial facility designed to prevent misuse or misappropriation by anyone in the general public.
by Tom Pullizzi, CEF, email firstname.lastname@example.org
Potential uses/Special properties of Tin Nickel electroplate
Developed in the 1950's. Dr. Parkinson, inventor, at Tin Research Institute in Middlesex, England
Recycling of Rinses, Dragout - Do not recycle because of precipitated tin
No agitation required, keep aeration to absolute minimum to reduce formation of stannic tin.
temperature: 150 minimum - 154 degrees Farenheit
material of construction of tank and plant - highly corrosive solution, contact vendors of plating plant.
anodes - rolled, depolarized nickel anodes and tin anodes (double bag tin anodes), tin chloride added to make up tin.
filters and bagging of anodes - Orlon
filters, plastic or stainless steel
Definition of "fanning/color buffing", which is performed on a buffing wheel as described in L. Morin's tape.
Use lime on an open weave buffing wheel, removes tin, polishes the surface and enhances the pink color of the deposit.
fingerprints easily because of attraction to organics, use cotton gloves.
Analysis of nickel and tin
Analysis is by simple titration. Both Langford and Parker and the Metal Finishing Guidebook show the same procedures. Control of other additives is by pH and Hull Cell analysis.
Control parameters of the solution
current density: 25 ASF maximum
nickel chloride 40 ounces per gallon (opg)
ammonium biflouride makeup 7.5 opg
tin chloride 6.5 opg
Keep within 90 to 100 percent of this cencentration by analysis. and nickel and tin chloride for maintenance
Grain refiner control: sodium fluoride is 2 opg as makeup, Daily Hull Cell test.
Hoeing up: stratification of solution - hoe up the solution 2/3 down up and down 1/2 dozen times, heavy stuff will settle and no more hoeing is required for the rest of the shift. In a half hour, all solids will settle and the tank should run the rest of the day.
ammonium biflouride makeup: 7.5 opg. Control during use by use of pH Hydrion pH paper. 2.5 - 2.8 pH, low add ammonium hydroxide, if high add ammonium bifluoride.
Carbon treatment and dummying are not necessary. It is important to keep oils and other organics out of the plating tank by use of previous cleaning and rinsing steps.
Solution Maintenance: keep at 90 to 100% of makeup for nickel and tin, control pH to within NaF is the brightener and grain refiner. Hull Cell test, 1 amp, 10 minutes, 150F. should be bright to 25 ASF. Burn free to 40 ASF.
stannic tin removed by pumping solution at 150F to a treatment tank, filter back into cleaned plating tank at 100 F using a 10 micron filter.
Rack plating - 0.5 to 1.5 volts, do not need cathode rod agitation.
Shelf roughness caused by stannic tin, see hoeing up porcedure.
keep barrel well submerged to prevent aerating the solution
Post plating steps: after plating, 10% ambient temperature HCl, 30 seconds or less, the white cloud is the stannic tin (if you dehydrate the salt, you will need boiling HCl to remove it), follow by rinse, rinse in water.
Wise to use a gold chloride strike before gold
cyanide gold cathodic 4.5 V 30 sec
acid gold without gold chloride strike, go direct at HCD, 7 millionths of an inch, only needed for solderability, shelf life, moving line contact, more lubricous than indium alloy gold would be. PCB connector tabs.
More information about plating teapots, with the handles and spouts. If you have copper based alloy part with this kind of high and low current density areas, think about tin-nickel plating to forget about shields, robbers, internal or special anodes.
Reactivation of nickel: immersion in the tin-nickel solution without current.
fingerprints don't show as much on a curved surface.
Special Procedure for making anode connections for submerged fluoborate plating solution where anodes are submerged in a fluoborate plating solution (listen to podcast for L. Morin's description)
drill and tap copper terminal 1 inch square stock, one half 3/8-16 turned screw on one side. the other half a socket hole. Tin nickel this piece to 5 microns thickness.
vinyl insulated welding cable, trim the line cleanly. solder dip the end of the wire and solder into throat of the tin nickel plated brass piece.
Use rack coating touchup masking to cover solder area, use to terminate in fluoborate coating solutions under the solution. This connection should last for the life of the anode.
Just a few questions that have been answered in Lou Morin's excellent discourse about tin-nickel plating from the chloride-fluoride bath:
Why would you put a copper strike under the tin nickel plate?
Why would you put a tin nickel deposit in boiling concentrated phosphoric acid?
What is the main problem with plating thick deposits of tin-nickel?
What was the application of tin-nickel in electric percolators?
How did Mr. Morin demonstrate the amazing throwing power of this solution to customers?
What are the two functions of sodium fluoride in tin nickel plating?
How do you control the grain refiner in the bath?
What voltages would you expect in barrrel and rack plating?
What are the materials of choice for heating coils?
How do you maintain the anodes?
How do you maintain the bath for stannic tin?
How corrosion resistant is this deposit; several surprising examples
These and many more are discussed in the podcasts, don't miss them!