E-Nickel and Corrosion

[kritter]

Im looking for recomendations on an E-nickel spec.

Im designing a mono tube shock absorber for the aftermarket truck industry and the call out I am using thus far for prototypes is:

Mid P 7% .0005 inch thick

High P 11% .0005 inch thick

I sent them out for corrosion testing and at 24 hours the 11% was trashed and the 7% was showing some red rust in the threads which im told is where rust will start. I know some competitors are using E-nickel on there shock bodies. After having the competitiors x rayed the thickness shows 3-5 tenths, but the company wasnt able to tell me with 100% faith, the exact chemical make up since the machine was telling them 7%P in some spots and 11%P in others.

I would prefer this piece did not rust at all in the field.

What E-nickel spec should I be looking at and what would be a good salt spray test hour wise?

Currently they were tested to ASTM B733(03) 5% solution at 95 degrees F for 24 hours.

This is my first time dealing with plating and it was brought upon me due to purchasing going blindly with what was cheap and it failed on the show vehicles we have these shocks on which took one trip back east (4000+ miles round trip) in the rain and snow. I have learned a lot on my own but I just need some help figuring out what real life is compared to these tests as well as if my plating needs to be beefed up and how.

Adhesion was not an issue as I had samples tested for adhesion as well.

 

[Carburize]

It has been a long time since I had any direct dealings with electroless nickel plated components but I recall that we used to use 0.0005-inch for mild corrosion service, 0.001-inch for moderate and 0.003-inch for severe service. We used to specify 11.5% minimum P 13% maximum.
I'm sure some of the current users will be able to add significantly more detail but I would have thought that your environment needs more than 0.0005-inch of thickness.

 

[kritter]

I went down to the platers and showed them the results of a 24 hr test.

A last step in their process is a dip in ultra seal which I belive is some kind of silica something coating. When I told him what we have now from 24 hrs is not gonna cut it he suggested a chromate dip for the last process instead of the ultraseal.

adding .001" of plating seems extreme to me...more input would be great.

Thanks

 

[mqas]

Kritter,

My experience of E-Nickel is as a manufacturer supplying to the Oil & Gas industry.

Standard in O&G is >10% P for corrosion resistance based on work done by Shell. <10% the coating was generally used for mild wear resistance.

Thicknesses in O&G vary but for corrosion resistance 0.003" minimum is standard (again based on Shell) although some manufacturers maintain 0.001" is sufficient.

I never got a low P coating or 0.001" coating to pass a salt spray test. The Chromate passivation as the final process will help obtain good results in the salt spay test, but it can also mask evidence of pitting which can be quite common in low thickness E-Nickel coatings. Make sure the coating is Ferroxyl tested as this will highlight any pores in the coating and will give an indication of how good the coating really is prior to salt spray testing.

I found the best source of knowledge to be the chemical suppliers to the plating shop or the surface finishing association as they had spend a lot of time and money in R&D. I could supply more info. on these but they would be UK based but they may be of use so please let me know.

Lastly, there can be a wide variation in the P results obtained from chemical analysis of such coatings, depending on the analysis method and again it is best to seek advise from the chemical suppliers.

Trust this is of use.

 

[EdStainless]

Was this given any thermal treatment? You know that eNi will age harden to very impressive numbers (the high P). This may have an impact on the corrosion that you are seeing. As I recall the aged condition was better, but it has been 30 years so don't quote me on that.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[israelkk]

Look for MIL-DTL-26074F COATINGS, ELECTROLESS NICKEL REQUIREMENTS FOR.

at

http://assist.daps.dla.mil/quicksearch/

 

[Carburize]

EdStainless - the as-deposited condition has the best corrosion resistance - heat treatment will produce a hardening of the electroless nickel but the corrosion resistance is not as good.