2025 Poster Session

This project investigates the retreatablility of mild steel in a marine environment with a selection of conservation and proprietary adhesives after a corrosion inhibitor, Ship-2-Shore (S2S), has been applied. S2S is an oily, calcium sulfonate-based “dewatering fluid” that penetrates vulnerable areas and displaces moisture. Corroding steel will often delaminate and detach requiring consolidation methods that are compatible with this barrier-like corrosion inhibitor.

The locus of this exposed steel is a 60’ x 60’ portion of the Slurry Wall. This reinforced concrete architectural feature is an archaeological remnant of the original retaining wall responsible for holding back the Hudson River during excavation of the original World Trade Center site. It now remains preserved in situ as the 9/11 Memorial Museum’s largest artifact. In the aftermath of 9/11, steel cables (tiebacks) were installed to stabilize and temporarily anchor the wall into bedrock during the site recovery. Though the Slurry Wall no longer performs a structural function, the tiebacks and their steel caps remain visible on the surface, continuously exposed to brackish water infiltration that was a feature of the wall since its inception.

Displaying a former structural element in a dynamic environment brings some conservation challenges. Reinforced concrete has an expected use life, and water ingress    poses a continuing risk to the tiebacks. A five-year investigation of the structural integrity of the wall and conservation triage identified the corrosion and delamination of the tiebacks as a significant concern. After research into a variety of corrosion inhibitors that would function in this unique environment, half of the exposed tiebacks were treated with S2S. Although appearing to have mitigated the corrosion, S2S does not secure delaminating fragments. The proposed plan is to re-adhere lifting pieces before they detach. However, whether the S2S will interfere with curing and adhesive properties needs to be determined before implementation of any treatment plan. When one emergency is over, how do you plan for the next? Small-scale testing may help form the answer   for ongoing care.

A DeFelsko PosiTest® AT Pull-off Adhesion Tester was used to quantify and compare the efficacy of 12 adhesives applied to both S2S-coated and uncoated steel plates in humid and ambient environmental conditions in laboratory setup. Graphs of the tensile strength data and detail images of the failed test joins reveal a marked and surprising difference in the performance of the various adhesives. Alkyd-compatible acrylic resins (Paraloid B-67, Plexigum PQ-611) in nonpolar solvents adhered best to the oily S2S surface without displacing the coating and allowing the formation of rust. A narrowed field of adhesives will determine the effects of additional parameters on relative tensile bond strength: adhesive concentrations, solvents selection, pre-corroded surface topographies, and cure time of the coating before adhesive application.

These tests inform an ideal treatment protocol for corroded steel that is consistently exposed to moisture and wet-dry cycles by balancing corrosion protection with surface integrity.   Simulating maintenance treatments expected in future years builds a better understanding of how the metal, coating, and adhesive interact and prepares for next necessary interventions.