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Diving Knife Corrosion Protection

We are making diving knives in 420 SUS stainless. They are finished with a triple coat CVD Titanium. We are getting very bad rusting due to people not cleaning the knives after submersion in the seawater. Will electroless Nickel plating (with nickel strike pretreatment) of about 10 micron improve our corrosion resistance?

Jack Nissen
Trading Company - Johannesburg, South Africa
2005

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2005

EN will probably improve the performance of your drives. You are probably experiencing galvanic corrosion between the 420SS and Ti as well as regular seawater corrosion. The potential difference between 420 and Ti is about 500 mv with Ti much more noble. Thus any pores through to the 420 will be rapidly corroded.

The potential between 420 and EN is only about 200 mv which probably is not enough to initiate galvanic attack (usually you need 250-300 mv difference for galvanic corrosion to occur).

Ron Duncan [deceased]
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.

Just how thick is that "triple coat" of CVD titanium you say? But yes, 10 or preferably 20-25 microns of EN will give you a good life regardless of rinses. Make sure it's high phosphorous w/o hardening at high temperature.

Guillermo Marrufo
Monterrey, NL, Mexico
2005