Nickel plating anticipated salt spray test hours

A. Please try with following combination

Base material + Copper (4 to 5 microns) + Ni (15 microns) + chrome flash.

We have carried the salt spray test on the base material steel with combination and our part is passed for 96 hours.

Best of luck.

A. I don't think there's a problem if you can cyanide copper plate first to a thickness of 15 microns before nickel plating. It will also give you better corrosion resistance.

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A. Please try the following :

• Cleaning
• Cyanide Cu Strike
• Semi-bright Nickel (60% of total Ni)
• Bright Nickel (40% of total Ni)
• Chrome

Critical is the duplex nickel with a potential difference of approx. 100mV.

A. Hi, Ahmed.

We've appended your inquiry to a thread that may help answer it (see also letter 53155 "To Pass 24 hours of Neutral Salt Spray Test in Nickel and Chrome Plating"). It strikes me that the fact that you are able to get 24 hours from your current process is good, and serves as evidence that your process is under control -- but that a single layer of nickel 12 microns thick is not up to the task, and you must use a copper undercoat, or duplex nickel, or substantially thicker nickel. Good luck.

Regards,

A. 3 min in a chrome tank is barely enough to get color. You will get zero corrosion resistance from that amount. So, You are looking at nickel having to do the job and 12 micron will rarely do the job, even with electroless nickel.

A. Hi,

Read what chemical you have and try to understand why your deposit will corrode. After that I will explain for you why the deposit will corrode.

Regards,

A. Hi Pavan. Yes, MIL-DTL-5541 [on DLA] "TCP", properly done on type 6061 aluminum, can pass 168 hour salt spray test. But I have no idea whether doing this process on the boxes will suit the needs of the power transistor modules.

Nickel plating is more reflective than conversion coated aluminum, but it is a barrier layer plating on a more active substrate (the reverse of providing cathodic protection, the aluminum will corrode to protect the nickel plating if the aluminum is exposed by porosity or pinholes). If you choose to nickel plate aluminum, you must choose to plate it really well.

Regards,

A. Hi Chandrasekhar. Unfortunately: zero hours un-annealed, zero hours annealed :-(

Nickel plating is cathodic to steel, which means it is solely a barrier layer which is only capable of protecting steel if it is non-porous and free of pinholes. If there is porosity or pinholes, nickel plating will accelerate the corrosion of the underlying steel, rather than retard it. And there probably will be porosity and pinholes in a 3 micron coating.

Is there a reason this narrow and very thin strip can't be stainless steel instead?

Regards,

Q. Sir,
The strip mentioned is used in Ni-Cd Pocket plate Battery electrodes.
I understand that porosity of plating is an important factor in resistance against rust / corrosion.
But then CORUS SPECIAL STEEL (CSS Germany) is making battery grade strip with just 2 microns nickel plating on cold rolled steel adding diffusion annealing to the plating process.

"Hilumin is an electrolytically nickel-plated, diffusion annealed cold-rolled steel strip whose benefits are appreciated by many international manufacturers"

Whereas we are doing 3 microns nickel plating without annealing and we have the problem of rust catching frequently.
How then is it possible?
Regards,
chandrasekhar

A. Thanks for explaining the situation Chandrasekhar! I thought you were talking about annealing the metal before plating; I didn't realize that you were speaking about a diffusion baking process after the plating.

This baking process diffuses the porous cathodic coating of nickel on steel, forming instead a nickel-iron alloy which can presumably be free of pinholes & porosity, while offering an electrochemical potential which is closer to steel and not as galvanically aggressive towards it as pure nickel plating. So again, whereas 3 microns unannealed will not be enough to be non-porous and pinhole-free, 2 microns annealed may form a reliable nickel-iron alloy.

But, sorry, I have no experience with its salt spray resistance. Hopefully another reader is familiar with it.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 29, 2013

A. Hi Kelly. Top quality copper-nickel-chrome plating will easily last 5 years in the worst environments. 15 years or more is possible. But salt spray testing may not be appropriate. Look into CASS or Corrodkote testing as they were designed to be better indicators of the quality of nickel-chrome plating. Good luck.

Regards,

A. Do you do passivation after plating?
If you just want to meet 96H salt spray test, I suggest to add passivation process.

A. Hi cousin Gagan. Nickel is often deposited from 10 to 40 microns thick on steel per some established standards, but might be even a bit thinner for an inexpensive decorative application, and a Wood's Nickel strike on stainless steel is vanishingly thin.

If you can explain your actual situation readers can usually help you decide what to do for that one particular situation.

Please try to take this is the right spirit, but we often get questions that sort of say: help me be able to choose for myself the right electroplating material and the right thickness for various situations ... but the real situation is that plating consultants earn their living helping customers make design choices, but usually only after acquiring 20-50 years of broad experience :-)

Your best approach might be to get some standard plating specifications from AMS, ASTM, ISO or whatever and see if they give you insights into what you need.

Regards,

A. Hi Hans. We are having a bit of language difficulty: I don't know what a thickness of "1200 micrometers" means. But I think I understand that you are nickel electroplating ductile iron castings and you want to salt spray test them for 168 hours, believing that this is equivalent to 40 years of real-life corrosion.

I think my reply is that 168 hours salt spray resistance can probably be obtained with high quality nickel sulphamate nickel plating onto vacuum-impregnated ductile or otherwise properly treated high quality iron castings ... but there is no reliable relationship between salt spray hours and actual life, and 40 years is a darn long time! Top quality duplex nickel plating plus bright chrome will sometimes last 40 years on automobile brightwork, but certainly not always; on a ductile iron casting, almost surely not. Good luck.

Regards,

  Thank you Ted, at first I have to apologize: the targeted thickness is 1200 µm (1.2 mm). Your answer helped me well!

I will go with assumption and introduce the 168 hours (or longer) as a suitable test value. Knowing, there is no definite relation to the aim of 40 Years resistance duration. Probably I will try to find a correlation or a theoretical approach for this, but for this too, I know it is theoretical. Furthermore I will add a cavitation wear test (ASTM G32), to evaluate the quality of the above mentioned Nickel layer. Thanks for the hint with the special well preparing of the ductile iron surface.
I will continue reporting. Yours sincerely, Hans

A. Hi Mahesh. Energizer® suggests at least 200 µin [5 micrometers] for battery contacts, but this would probably last nowhere near 96 hours even on the very smooth surface we'd expect for a battery contact. As you see on this and related pages, 96 hours salt spray is a somewhat tough requirement for nickel plating because the plating must be pinhole & porosity-free -- so before investing in an elaborate plating sequence you might want to double check whether this much salt spray resistance is truly required for a battery contact. Further, how exactly would your inspectors decide how many hours the battery contacts "passed", since electrical conductivity rather than appearance is the actual requirement.

My strategy would probably be to try to talk the stakeholders into accepting some thickness in the 12 to 20 micron range :-)

Regards,

A. Dear Mr Mahesh,

I would suggest that you use three layers (Tri Nickel) plating with a minimum plating thickness of 25 microns.

A single layer of Nickel plating even up to 20 microns may not be entirely pore free.

best regards,