Hot-dip galvanized steel foundations demonstrate corrosion resistance over decades of field service Sponsored

Evaluations of hot-dip galvanized Chance® Instant Foundations installed in the early 1980s have confirmed continued structural performance after more than four decades in service. The foundations utilize steel components manufactured to ASTM galvanizing standards, with zinc coating thicknesses typically ranging from approximately 4 to 7 mils. The zinc coating functions as a sacrificial anode, corroding preferentially to protect the underlying steel, unlike paint-based coatings that may peel or sustain damage over time.

Two primary soil parameters are used to assess corrosion potential for buried steel foundations: soil resistivity and soil pH. Lower resistivity values indicate greater corrosion risk, while higher resistivity generally corresponds to lower corrosion potential. Soils with a neutral pH near 7 are considered less corrosive than acidic soils with pH values near 5 or below. According to Chance engineering guidance, well-draining soils with resistivity levels above approximately 2,000 ohm-cm can typically support a service life exceeding 50 years. That estimate reflects expected material loss remaining insufficient to compromise structural performance, rather than complete consumption of the zinc coating.

One documented case study involves a Chance Instant Foundation installed in December 1983 at the Gibson Substation in Centralia, Missouri. The foundation remained in service for more than 32 years before being excavated and analyzed in March 2016. The installation site presented challenging subsurface conditions, including surface gravel, brown clay soils, grey clay at helix depth, poor drainage, and saturated soil inside portions of the foundation during excavation. Researchers evaluated galvanizing thickness, examined corrosion patterns, and inspected the steel for material loss across the upper, middle, and lower shaft sections, as well as the helix and base plate regions.

Upon excavation and inspection, galvanizing remained present across the foundation. Corrosion was concentrated primarily near the lower shaft, helix, and base plate regions, while the upper and middle shaft sections showed minimal corrosion and no significant steel loss affecting structural performance. Discoloration observed on portions of the excavated foundation was determined not to be rust; scratching the surface revealed galvanizing still present beneath the outer layer. Historical galvanizing thicknesses for the foundation were estimated between 5 and 7 mils. Using the most conservative measurements recorded during inspection, engineers calculated a zinc loss rate of approximately 0.19 mils per year, indicating exceptionally slow corrosion progression under relatively challenging soil conditions.

The Centralia case is not the only documented long-term example. Chance documentation also references transmission line foundations installed in Minnesota's Tamarack Swamp in 1977, representing an additional long-term field installation in a demanding soil environment. Separately, Chance foundations currently still in use in Centralia, Missouri, were originally installed in the late 1960s, placing their service life at more than 50 years. Zinc remains visible on the base plate of those foundations, consistent with the corrosion rates recorded in the 2016 study.

These field installations collectively support the use of hot-dip galvanized steel foundation systems for lighting, utility, telecommunications, signage, and other infrastructure applications where long-term service life and low maintenance requirements are critical specification criteria.