Iron quality question??

[entsminger]

The other day we were at the river looking around and we came upon two huge iron boat moring rings about 2 inches thick. They are over 100 years old but show little if any deteriation or rust and are under water quite often. Right next to them are a few modern steel hunks that are rusted to pieces. I am hoping some of the metalurgy experts on this site can tell me what's up with this old iron being so indestructable. Is it because it's virgin iron and the new stuff is over used and weak or the way they were blacksmithed or what?? Do you think old cannons like origional civil war mortars were made from this same tough iron??

  Scott

[Cat Whisperer]

There are many 'flavors' of iron - alloys, percentages of carbon, etc.

In the 1960's some steels became popular for exposed structures that would rust to a point where the iron-oxide (rust) on the surface would provide a protective coating for the rest of the metal.

[kappullen]

I believe some of the old hand wrought irons were more rust resistant
because of some of the impurities and slag contained in the matereial.

Some wrought iron looks like wood from the grain in the material.

I re-machined some valve linkages and rods form a sunken steam tugboat (tugboat baltimore at the baltimore museum of industry) and the grain was very obvious.

This tug had spent several years sunk in the bay but is now the only operating steam tub on the east coast.

http://www.mdarchives.state.md.us/msa/mdmanual/01glance/html/port.html

kap

[GGaskill]

It is my understanding that pure iron does not rust, so maybe old wrought irons were rust resistant/non-rusting.  I don't think any steels (excepting chrome-nickel alloys and maybe copper-bearing alloys) are rust-free.