The U.S. Department of Commerce National Bureau of Standards ("NBS") states the following in their book titled NBS PAPERS ON UNDERGROUND CORROSION OF STEEL PILINGS:

Data obtained by the NBS on the corrosion performance of steel piles driven into the ground in a wide variety of soil environments show that the strength and useful life of steel piles are not significantly affected by corrosion. These findings are in sharp contrast to those of earlier corrosion studies in which iron and steel specimens, such as pipe, that are buried under "disturbed" soil conditions exhibit varying amounts of corrosion.


Steel pilings which have been in service in various underground structures for periods ranging between 7 and 40 years were inspected by pulling piles at 8 locations and making excavations to expose pile sections at 11 locations. The conditions at the sites varied widely, as indicated by the soil types which ranged from well-drained sands to impervious clays, soil resistivities which ranged from 300 ohm-cm to 50,200 ohm-cm, and soil pH which ranged from 2.3 to 8.6.

The data indicate that the type and amount of corrosion observed on the steel pilings driven into undisturbed natural soil, regardless of the soil characteristics and properties, is not sufficient to significantly affect the strength or useful life of pilings as load-bearing structures.

Moderate corrosion occurred on several piles exposed to fill soils which were above the water table level or in the water table zone. At these levels the pile sections are accessible if the need for protection should be deemed necessary.

It was observed that soil environments which are severely corrosive to iron and steel, buried under disturbed conditions in excavated trenches, were not corrosive to steel pilings driven in the undisturbed soil. The difference in corrosion is attributed to the differences in oxygen concentration. The data indicate that undisturbed soils are so deficient in oxygen at levels a few feet below the ground line or below the water table zone, that steel pilings are not appreciably affected by corrosion, regardless of the soil types or the soil properties. Properties of soil, such as type, drainage, resistivity, pH or chemical composition, are of no practical value in determining the corrosiveness of soils toward steel pilings driven underground. This is contrary to everything previously published on specimens exposed in disturbed soils but does not apply to steel pilings which are driven in undisturbed soils.


The observations reported in this paper are in agreement with and substantiate the observations and conclusions based on the results of the previous examinations on steel pile structures which are published in NBS Monograph 58.

The data show that, in general, steel pilings are not significantly affected by corrosion in undisturbed natural soils, regardless of the soil types and soil properties. Only minor or moderate corrosion in the form of shallow metal attack or localized pitting occurred on the upper portions of the pile structures which were exposed in fill or in soils above or in the water table zone. The average reduction in wall thickness on any of the piles examined was not of sufficient significance to impair the useful life of the structures.

...The difference in corrosion was attributed to the differences in oxygen concentration. It was indicated that undisturbed soils are so deficient in oxygen at levels a few feet below the ground line, or in and below the water table zone, that steel pilings re not appreciably affected by corrosion, regardless of the soil types or the soil properties.

The National Association of Engineers ("NACE") publication titled "Corrosion Basics" makes these statements pertaining to corrosion and coatings:

NACE pg 216
An important difference with steel piling is that a few pits or even holes have little effect on its structural strength. Consequently, much more corrosion can be tolerated than with pipelines. Piling is almost always bare, vertical, and hence subject to the same kinds of cells that attack oil well casings. Bonding often may be a problem because individual piles may not be interconnected electrically, a condition that makes both investigation and protection a problem.

NACE pg 216
Galvanized steel is not normally installed underground. The thin zinc coating is quickly dissipated by galvanic action with any exposed steel.

NACE pg 213
An obvious method of controlling corrosion is that of interposing a barrier between the threatened metal surface and the corrosive medium, i.e. some kind of coating. Since corrosion always requires the presence of an electrolyte (moisture) in contact with the metal, if a metal could be coated with a material which was absolutely waterproof and absolutely free from holes, all attacks would be stopped. The coating, it should be noted, would not only need these two properties when it was applied, but the two properties would have to be permanent -- the coating would have to remain perfect in both respects.

NACE pg 238
As soon as a pore or bare spot appears, the corrosion of the base metal is accelerated.

NACE pg 266
A coating may fail as a result of a large number of potentially adverse conditions. Some of these can be defined as mechanical, as when abrasion or impact removes the coating.

The previous information shows clearly that coatings on steel piers do not effectively increase its life expectancy. It may in fact, due to abrading that occurs in coatings of driven piers, "actually decrease its life expectancy".

Both the NACE and NBS publications cover corrosion and protection information in much greater detail than we have shown here. What we attempted to show were some excerpts that pertain to driven steel piers.

The Perma Jack pier's load-carrying ability actually increases with time. The reason for this is called "Thixotrophy". The definition is:

"Particles attempting to reoccupy the space from which they were removed."

This applies to the soil that is displaced by driving the pier that wants to reoccupy the space now taken up by the pier. This returning soil grabs the wall of the pier, greatly increasing the frictional support.

This is evident even in very short periods of time, such as overnight. A pier started and driving at a given pressure left to sit overnight may require 50% to 100% more pressure to begin driving again the next day. This additional pressure varies greatly due to varying soil conditions. Although this frictional support of the soils adherence to the wall of the pier is not counted on, it adds another safety factor to the system.

Southern/Austin, Inc., 9514 McNeil Rd., Suite 101, Austin, Texas 78758, Phone: 512-419-1600, Toll-free: 800-840-7989, Fax: 512-973-8679