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topic 57029

Recommended corrosion protection finish for 4340 steel

A discussion started in 2011 but continuing through 2018

April 12, 2011

Q. I am designing a tie-rod, a 1 meter long 14 mm diameter rod with a 30 mm threaded section at each end.
The material is is 4340 steel and the tie-rod will be used outdoors.

What finishing treatment should I specify to protect the tie-rod against corrosion?

The objective is to give maximal protection without compromising the strength of the rod.


Avner Bronfeld
Mechanical Engineer - Givataim, Israel

April , 2011

A. Hi, Avner.

Galvanizing is usually considered the best treatment for outdoor exposure, but I just read an article claiming that it embrittles 4340 steel. A zinc alloy electroplating like zinc-nickel with a chromate conversion coat ought to be pretty good. Electroless nickel is a possibility, but expensive.


Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

simultaneous April 13, 2011

A. IVD aluminum is another possibility. The military is using IVD aluminum to replace cadmium plating.

jim treglio portrait
Jim Treglio
PVD Consultant - San Diego, California

April 13, 2011

A. Electroplating on 4340 is also embrittling. Zinc-Nickel is not generally recommended for high strength steels like 4340, although there some newer specialty formulations used pretty much exclusively in aerospace applications. Regardless of the plating that you choose, you should follow the plating operation with an embrittlement relief bake. Usually 375 °F for a number of hours.

Jon Barrows
Jon Barrows, MSF, EHSSC
Springfield, Missouri

April 15, 2011

A. Paint them. Use a specific primer for SS and a good quality stuff like automotive paint. Easy, cheap, durable and nice looking. End of story.
G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico

May 20, 2018

Q. What corrosion protection is best suited when using 4340 steel as a roller shaft that is subject to corrosive fertilisers and moisture where a bearing and seal is used on each end of the shaft.

ray dufty
- gold coast australia

May 2018

A. Hi Ray. It probably depends on what the overall product is and how exotic and expensive you want to get, and what kind of bearings you have in mind.

Cheap would be put masking caps on the ends, paint as suggested by Guillermo, remove the caps and press the bearings on, ignoring the potential for corrosion under the sealed ball bearings, or using oil impregnated bronze bearings instead.

More exotic solutions might be electroless nickel plating, or thermal diffusion zinc coating, but if this is some kind of inexpensive fertilizer spreader where the bin and everything else is going to corrode away in two years anyway, an exotic roller system may be overkill. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

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