plating, anodizing, & finishing Q&As since 1989
Electroless nickel plating on cast iron parts
January 29, 2010
Q. Dear Sirs,
My name is George Ivanov and I'm heat treatment and coating technologist in company in Bulgaria. Our company manufactures hydraulic motors and steering units - www.ms-hydraulic.com . I suggest to my managers to put electroless nickel plating 20-25 microns onto our hydraulic motors.
After coating we carried out Salt Spray test (NSS - 400 hours) and the results were not so good. I have found that all steel and cast iron parts, which were machined (by turning or milling, they were perfect (without any corrosion). But the cast surfaces, which are not machined were coated with corrosion. Nickel plating coating is very uniform and without any cracks and defects.
That is my problem and I ask you to advise me :
1. How I can coat non-machined cast surfaces with nickel for corrosion protection ?
2. What do I have to do before coating to improve corrosion resistance of the nickel coating ?
engineer - Kazanlak, Bulgaria
January 30, 2010
A. Oxides from the casting process are thick and tenacious. An initial mechanical cleaning (sand blasting) before machining sounds like a good start. Also, find out what lubricants or coolants are being used during machining. Your pre-cleaners must be able to handle them. Good luck.Guillermo Marrufo
Monterrey, NL, Mexico
February 2, 2010|
On the cast surface, which is not machined, there is no rust or oxides, it seems to be sand blasted after casting process, but I will try sand blasting or shot peening again. About lubricants and cooling liquids during machining we have been using semi-synthetic liquids - Houghton products and after machining we clean these parts by alkaline solution in spraying washing machines and before assembling we have manganese phosphating process.
- Kazanlak, Bulgaria
February 2, 2010
Aerospace - Yeovil, Somerset, UK
February 16, 2010
Q. Dear Brian,
Sorry for this late answer, but I was in holiday last weeks.
About your questions:
1. We use middle phosphorus(5%)nickel plating process
2. prior stage of plating is alkaline degreasing by immersing - temperature 60°C
3. The rust looks like as many spots and small lines, there is no full surface coverage on the cast part. It mean that the rusted surface is about 15%.
Thank you for your advice, but we make this process in other company I have to ask this company to implement your suggestion.
If they couldn't make this process what is your advice ?
- Kazanak, Bulgaria
February 17, 2010
My first advice would be to change to a high phosphorus coating (10-14% P). Lower than this means that you may not get the desired level of corrosion resistance.
Secondly, I would certainly consider using a thickness of 50 microns if want a good corrosion resistant coating.
There is one other thing you could consider doing (but don't do this if you need to be RoHS compliant) and that is to carry out a 5% chromic acid wash (CrO3). This will impart a certain amount of corrosion resistance, not a great amount, but it might be the difference between passing and failing.
Finally, your description of the failure mode certainly indicates to me that the failure is more likely due to thickness issues rather than pre-treatment issues. I think that your pre-treatment is probably sufficient for what you are doing, although the surface can never be "too clean".
Hope this helps on a way forward.
Aerospace - Yeovil, Somerset, UK
February 9, 2017
Q. I'm a student and I want to know some details for doing my project:
1. Does electroless nickel plating on cast iron have good corrosion resistance and heat withstanding properties?
2. If it is suitable, what's the composition of product?
3. Is electroless nickel plating powder enough for coating?
4. Which material composition is best for coating 20 cm dia cast iron
5. Or what coating Will best suit for cast iron?
- Chennai, tamilnadu, India
A. Hi Yogesh. What is the product that you envision plating and why? What is the environment? The wear situation?
Trying to answer your questions in the abstract is just very misleading because, for example, do you know that the electroless nickel plating will probably cost you something like 10X as much as electrolytic nickel plating? Maybe that's not a problem, but maybe it's a total deal killer and you're wasting your effort.
2. 86-96% nickel, 4-14% phosphorous, more or less.
3. No, you need a proprietary electroless nickel solution, or a lot of ingredients.
4. Not answerable in the abstract.
5. Not answerable in the abstract.
Good luck, and Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey