protection for buried steel

[dison]

I am seeking opinions and/or recommended sources of information on the following:

What would be the best method to protect steel from corrosion when it is buried in soil in a location where both moisture and oxygen would be available to promote the corrosion? For the sake of making a comparison, use a long term design life (say 100 years) and a non-reactive soil (no chlorides, etc). Use of additional steel thickness to offset loss due to corrosion? Galvanizing? Painting? Epoxy coating? Specialized paint application? Asphalt or other roof coating material? Concrete cover? Cathodic protection? A combination of protection methods? ~dison

 

[mcguire]

It sounds like you could use some stainless steel. No protective measure is going to be effective for the time period you cite. A lot depends on what it is you're putting undergroung and what it needs to do...contain toxic materials or just sit there.
316 stainless should do just fine.

 

[rustbuster]

I would condsider coatings, tapewrap, yellow jacket in conjunction with cathodic protection.

I would not bury stainless steels. They rely on O2 for passivation. Differentials in aeration and soil resistivity / conditions could lead to rapid corrosion. Especially at soil to air interfaces.

 

[mcguire]

Stainless does not require exposure to air to passivate. Any moisture will do the trick. The passive film is not an oxide, but an hydroxide.
Burying it will be fine. The same general rules of watching pH and chloride level have to be obeyed and essentially infinite design life can projected.
Sacrificial anodes won't last and organic coating won't make it to 100 years.
Go stainless.