plating, anodizing, & finishing Q&As since 1989
Salt fog expectations for electroless nickel plating, B4C, black oxide, Raydent coatings
Q. Hi! I want to learn salt fog test results for electroless nickel plating for steels (particularly 4340, nitrided).
I wanted to learn test results of salt fog tests for B4C (boron carbide), black oxide and Raydent coatings on steel. Can you help me? Thanks for your assistance.
August 17, 2017
A. Hi Ekin,
Could you frame your query in real-life expectations? What are the products you want coated? What conditions of use will they see? What do you expect the salt spray results to tell you?
The one thing to remember about salt spray is that it does not reflect real time life in the field, the only thing that does that truly is weathering trials, which is some cases can take years.
As a general guide Electroless nickel, high phosphorus at 0.002" thick will pass a 72 hour salt spray. Black oxide coatings with a supplementary chromate treatment would be expected to last 1 1/2 hours, but to be honest these numbers mean nothing other than a guide to the quality of the process applying the coating.
Aerospace - Yeovil, Somerset, UK
A. Hi. Brian is right on. Salt spray testing is actually a QA early warning test: if the coating used to pass XX hours of salt spray and it no longer does, something changed and went south in the process.
Picking a surface treatment based on salt spray hours simply doesn't work: a mediocre paint job will surpass any metallic coating ... whereas in reality, for example, hot dip galvanizing (despite its poor salt spray performance) can often last 75 years and more without maintenance -- world's better than numerous finishes that surpass it in salt spray hours.
Apologies but we cannot post comments on proprietary coatings like Raydent on this no-registration required website ( huh? why?)
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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