Electroless nickel plating peels off of 4340 steel

? Hi Palanisamy. I'm not familiar with type 3410 steel. Is this perhaps a typo? :-(

Please get back to us with whether you are dealing with 4310, 4340, 3410, or something else. Thanks!

Regards,

A. Are you activating first with acid nickel strike, either Woods or acid sulfamate?

A. Peel off of any plating is normally either the part is not clean or it is not properly activated. Clean 4340 is simple to plate.

A. Cracks may develop in the plated EN which has only about 1-2% elongation resulting in notch effect.

A. All 4000 series alloys should be nickel chloride struck first; then the EN should be no problem.

A. In the distant past, we plated 4340 with EN with no problems. Notch bar test slugs were a lot higher strength than that. We did get the parts into the bake oven as soon as possible after the rinse and blow-down. We used a standard of not more than 15 min from coming out of the EN to being in the oven. Also, acid etch was an absolute minimum. We used wet blast wherever we could and used a 10 sec dip in the acid.

A. Nickel Chloride strike is the best. 2 pounds per gallon nickel chloride, 32 fluid ounces per gallon Hydrochloric Acid, Rolled Depolarized nickel anodes (NOT S-rounds) taken out when not in use. Control the metal low. If you leave the anodes the metal content in the solution converts from and Inefficient strike into an Efficient plating bath and it starts peeling off again. Bag the RD anodes. Again, keep the metal low and the acid high!

A. Geoff Slater,

You want to plate 400 series steel part. The best method is following step.
1. soak cleaner
2. electrocleaner- Reverse current
3. rinse
4. 35-40% Hydrochloric acid dip
5. rinse
6. wood nickel strike
7. rinse
8. watt nickel

A. Geoff,
At that hardness level, hydrogen embrittlement will definitely be an issue and you will need to incorporate a baking cycle in your procedure.

Details of the most appropriate plating baths and types are outside my area.

Popatbhai,
Geoff wishes to plate 4340 steel, which is a high-hardenability low-alloy steel and is in no way related to the 400 series of stainless steels.

A. You are using the best pretreatment process for 4340 steel. Electro etching with sulfuric is an excellent method to remove any carbon smut from high carbon steels, like 4340, and provide a clean surface for adhesion. Nickel strike is a good insurance step. If woods strike is a question due to hydrochloric acid, you may want to consider using a sulfamate nickel strike. Much lower in HCl content and provides the same level of activation. A good practice when using a nickel strike is to enter the solution with a hot lead attached so striking begins as soon as part enters the solution.

No way to eliminate hydrogen embrittlement when electroplating using your process. Just incorporate a bake cycle after plating for hydrogen relief.

A. Hi Ramnah. I'm not sure that I followed your question properly. Are you saying that you successfully plated for 9 months, and after 9 months of successful operation this problem began?

Since you are now having problems both with your high phosphorous nickel and low phosphorous nickel, it seems unlikely that the chemistry on both processes has gone bad. Rather, it's a raw material problem or (probably more likely) a cleaning and activation problem.

But you will need to supply several paragraphs of detail before anyone can hazard any specific guesses of what has gone wrong. Is the material type 4340 steel?What are the types of parts, what mechanical operations precede plating, what is your mechanical and chemical cleaning and activation regimen? What are you aware of changing in the last month or so? Thanks.

Regards,

A. Hi Ramnah. I am not familiar with "S1040" and "P1051" -- I assume they are proprietaries from a local chemical supplier. But I am surprised that you achieved robust and reliable adhesion on a leaded steel without the use of hydrofluoric acid or a fluoride-bearing acid. In the nine months of good performance did you conduct any adhesion tests?

Regards,

A. Good day Paul.

I would focus on the heat treat/tempering/quench operations. I would also think that the acid soak would need to be more aggressive. What is the make-up? Perhaps the Wood's strike also needs to be addressed as longer time. What is the ASF? Suppliers can vary in procedural processes of metal stock, as you are well aware.
Hope this helps.

Regards,

A. Hi. Eric offers good points, but I think I'd focus on Robert Probert's first.

Regards,

Hi. Thanks both for your input. I have changed my pre-treatment Chemistry, so its a new batch. They are Dry products from my chemical supplier in the uk. The degrease is Electrolytic hot alkaline, at 55 degrees. The manufacturer recommendation is 25 to 75 g/l we run it at 50 g/l.
The Dry acid salts are at ambient temperature for ferrous substrate the recommendation is 50 to 75 g/l we run at 63 g/l.

The nickel strike is made up to a german formulation as it originally was part of my automatic German plating machine. This is 1.6 kg/10 Liters Nickel Chloride and 1.6 L/10L HCl.

Having read the earlier comments about the nickel strike, I am becoming suspicious this may be the problem area. We never remove anodes from it and it has now done quite a lot of work, with additions of HCl from time to time. I checked the S.G. and found it to be high. So without messing about analysing it, it will be cheaper and sound practice to replace it with new chemistry; the bath is quite small at 100L. I will keep you advised of my findings.

Incidentally, the steel has always been supplied in the T condition and has not been subjected to any further heat treatment.
Thanks all for your help.

Paul

A. Hi Muniraju. If the plating bath is operating properly, that is all the more reason to suspect inadequate cleaning or surface activation. But please check more exactly into what you mean by CRCA -- "cold rolled close annealed" might not guarantee that this is a lead-free, alloy-free, low carbon steel.

Please tell us the whole situation. Is this a brand new line and you have never successfully electroless nickel plated yet, or have you been doing it fine for decades but this one particular new part is giving you a problem, or what? Thanks.

Regards,