Iron vs Steel in Shipbuilding

Iron vs Steel in Shipbuilding

Olaf Engvig’s article on ironvs.

steel in shipbuilding was very interesting to me; I am a retired marine engineer with some kn owledge of wrought iron and steel.

I was, whar is called in the United States, a “port engineer,” and, as such, I arranged fo r and supervised drydocking of commercial vessels.

They were all steel hulls. O n o ne d rydocking in New York H arbor sometime in rhe early 1970s,

rhe vessel next to mine was a US Army Corp of Engineers dredge named Ezra Zanzibar.

Her port engineer and I spent coffee breaks together discussing our work and the quality of workmanship that we were each receiving from the shipyard. Borh sh ips were having steel hull plates replaced.

His vessel was a riveted wro ught-iron hull from the !are 1800s; mine was a World War II-vintage steel hull.

The decision to replace sreel plates in shipyard was based on thickness measurements, whi ch was a routine method in the 1970s.

He showed me where rhe original wrough t-iron plating on his ship was still in excellent condition with minimal thickness loss.

Wherever rhere was any damageJ hull plating, however, ir had to be replaced with steel because wroughr iron was not available anymore.

He pointed out rhar riveting a steel plare between wrought iro n set up a galvanic cell and only hastened rhe deterioration of rhe sreel .

He nored rhar these same sreel plates had been replaced befo re.

His vessel spent a large porti on of its time in fresh water, so the corrosion was not only due to saltwater service. You probably have heard many stories like this, but after reading Mr.

Engvig’s article, I had to bring one more story to your arrention.

There is a graveyard of 1800s wooden vessels burned to the waterline near where I live in New Jersey.

The noticeable remains on most of these are their rudder posts, which I assume were wrought iron.

I graduated from Kings Point in 1962 and we studied basic metallurgy there, but afrer rhe dozens of drydockings and hundreds of other repairs, you learn on-rhe-job merallurgy.

 Another example rhar I became intimate wirh was bronze propeller fa ilures.

A real old-rimer propeller repair shop owner pointed our rhar rhe T-2 ranker propeller that I senr in fo r rhe repair of a damaged blade tip had anorher problem.

He called ir “mud acid” (dark spors all over rhe bronze). Afrer losing entire blades off two of rhe T-2rankers rhar I rook care of,

I determined rhar rhe de-zincificarion (mud acid) was caused by rhe lack of good groundjng of the propeller shaft after installing a Brand X (cheap) impressed currenr system in place of zinc anodes on rhe srern frame.

One ship losr rhe blade our in to rhe ocean and limped in wirh grear vibration.

On the orher ship, rhe blade wenr righr rh rough the after peak rank.

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