Composite electroless nickel-PTFE plating

Hi Omidvar. Your situation is a little unclear to me. If you are trying to develop, introduce, and sell a process of your own, that's fine.

But sometimes researchers and students don't realize that the plating industry is full of well-developed commercial processes, and that plating is usually done from these proprietary processes, not from raw chemicals mixed up by each student. So, if you are just trying to get some parts coated, you can send them to a jobshop that offers that service, or simply buy a fully-developed process for in-house use - you don't have to invent it all over again. Again, it's fine to develop a competitive process of your own -- but we'd hate to put you through months or years of effort if you're just trying to get some parts coated :-)

Good luck.

Ted Mooney, P.E. RET finishing.com Brick, New Jersey

A. The co-deposition of PTFE with electroless nickel has been known for some decades, but the precise technology has been embroiled in either closely concealed commercial secrets or heavy patents. The patents are now starting to come to the end of their lives and there are more and more technical publications explaining the technology. You must do a thorough literature search to ensure you are up to date with the published technologies.

Successful co-deposition of PTFE and electroless nickel is dependent on many aspects of the process. Firstly, you have to get the PTFE into suspension; the ease by which this is done will depend on the particle size and molecular weight of the PTFE. Secondly, you have to make it hydrophilic; this is done with surfactants. Not only must it be hydrophilic, but it must be compatible with the electroless nickel process you intend to use. There are three type of surfactant, anionic, cationic and non-ionic - the selection of the correct type is essential to your success. Once you have selected your type of surfactant, you must make sure that it is the correct structure and chain length. As a start to your quest, a technical paper exactly on this subject has been published by Liu and Zhao in Transactions of the IMF, 81(5), 168-171. There are also numerous other papers in the technical literature. As far as I am aware, there is no one "magic bullet" that will work for all applications, so it is very much a "horse for courses" science, so you will have top sort out the process that works best for yourself, or get in a proven system form a commercial organization.

Trevor Crichton R&D practical scientist The Pheasantries - Chesham, U.K.

A. Dear Hamid,

First let me tell you that I have worked in this field. I will explain you very simply, you have two ways to deposit Ni-PTFE Composite coatings.

1- You can use the PTFE aqueous dispersion ready for use with required PTFE particle size which is available in the market but you have a main problem in this way, the Ni electroless bath is very dependent on the temperature and this type of PTFE dispersion which contains the surfactants are very sensitive to temperature too, because temperature more than 85 °C leads to agglomeration of PTFE particles and makes a problem in the process so it is very hard to do the deposition of Ni-PTFE coating in temperatures more than 85 °C and this is the limitation of this method. Also in this method, the Aqueous solution contains surfactants and as you know we have optimum level to use surfactants in the bath so if we use more aqueous dispersion in the bath, the excess amount of surfactants may have a sharp effect on electroless mechanism and prevent the coating process. This is a limitation too.

2-The better method is to provide the PTFE powder with required particle size and disperse it in bath solution with addition of suitable surfactant. Be aware that you should try different concentrations of surfactant to find the optimum level. This method is better than the first method, but it takes more time to disperse the PTFE particles in the bath.

A. I doubt you will be able to pass 1000 hours salt spray with 0.001" of combined EN+EN-PTFE. About your concerns, shower rinsing above the plating tank is a must. Careful design of your rinse (pressure, volume, temperature, rinsing time and constituents) will determine feasibility success.
Good Luck,
G. Marrufo