A magical corrosion proof, marine growth proof, strong metal. What was it?

Many years ago I taught science on the island of Guam. In the harbor you could dive to a Japanese dive bomber at a depth of about 30 feet. After 40 years of sitting upside down on the bottom of the sea the entire plane was a piece of junk. Marine growth covered it and profound corrosion had taken root. Except one surface, the hydraulic landing struts. Those two hydraulic rams were shiny as new with zero marine growth on them. No rusting, pitting, or discoloration of any kind were evident on those shafts. What magical formula was in that stainless steel? Did they use some toxic metal that industry can no longer use? I have always wondered about this, I see stainless rust all the time but those struts still perplex me after 30 years. Vibranium?

 

Was it chromed ? Not that I'm aware if Chromium resists growth.

 

It’s possible that the surface is too smooth for the marine growth to adhere to.

 

Hydraulic components are commonly chrome plated. It is very hard and wear resistant, very corrosion resistant, provides a smooth surface to seal against, highly toxic and very expensive.

 

Most likely a high titanium content in the surface treatment of the shaft isn't it?

 

Titanium is anti-biotic ? I know silver certainly is, I've seen silver coins dug up that have been buried a century, and shiny like new.

 

I'd put my money on chrome on the basis of its toxicity - I don't think titanium is particularly poisonous, and - I'm no historian, (or metallurgist, mind) but assuming this is a WW2 wreck, the vintage - didn't think titanium came in until a bit later?

 

Electroplating was a much higher standard around that vintage, I would guess that titanium would be laid at a particular temperature , like in a bearing case, I don't know which it is though.

 

Probably chrome, coated in hydraulic oil. I guess thats toxic enough to do the job.
There is no way it's titanium.
It was probably pitted and rotted, but in the sun, with all the rotted plane around it, it looked good and reflected well, but, if removed and brought up, would be found to have no intregity.

 

If the exterior of the rod is chrome plated, the substrate would have had to have had an electroless nickel plating process first. Chrome is subject to micro cracking ie porous. Being in a salt water environment the salt would have penetrated the
chrome and attached the base metal causing corrosion underneath it.

 

Copper nickel, "elements of boat building" Dave Gerr, at the end he talks about its longevity and that there is no need to anti foul, thanks Oldmulti for the download. It could be that the shafts were electroplated with more copper and nickel than in usual chrome plating.. Titanium was first used commercially by Du Pont in 1948. First military use was by Russia in 1960s, gee that interweb is handy.

 

this is incorrect..wrong..

 

Electroless Nickel
While most metal plating involves applying a direct electrical current to the object, in electroless nickel (EN) plating, the object reacts to the plating bath chemistry, creating a uniform and smooth, layer with very little surface porosity. The even deposition makes it an ideal choice for complex, non-line of sight, geometries and often eliminates grinding after plating. EN is applied to improve the corrosion and wear resistance of an object. Electroless nickel metal is a softer metal than chrome and can range from 40 to 60 HRC depending on the phosphorous content. Many times, a layer of hard chrome is applied over the nickel layer maximizing the objects ability to resist corrosion and wear.
re US Chrome

 

Monel or other CuproNickel alloy.

 

If the hydraulic piston casing remains intact, bio matter replacing gaskets and seals, that would help to electrically isolate the pistons from being part of a galvanic cell. The coating of hydraulic oil and the chrome casing help protect it.

I don't know about it's resistance to marine growth, but that sounds reasonable.

-Will (Dragonfly)