Abstract
This publication discloses methods and structures for applying corrosion‑resistant coatings to metallic wires and strips used as tensile and pressure armor elements in flexible pipe systems such as those defined in API 17J and API 15S (e.g., subsea, downhole, and annulus‑exposed environments). The coatings include fusion‑bonded epoxy (FBE), polyamide (e.g., PA11, PA12, and related thermoplastic polyamide families), and film/laminate constructs (e.g., XLPE with metallized or aluminum film layer, EVOH or PVDF-based multi layers), dual-layer systems (FBE primer + PA11 topcoat), nano-particle reinforced polymers (nanoclay-reinforced by PA11/PA12), and metallic-polymer hybrids (Zn-Al thermal spray combined with polymer overcoats). The disclosed approach focuses on directly coating steel armoring elements prior to pipe assembly to provide barriers against moisture and corrosive ions (e.g., Cl⁻, H₂S, CO₂), increase resistance to sour service, reduce under‑film corrosion, mitigate micro‑cracking and delamination under cyclic loading, and improve fatigue life. FBE is positioned for lower‑cost, less dynamic applications up to approximately 110–120 °C in the annulus offering strong adhesion and chemical resistance but limited flexibility under cyclic bending. Polyamide coatings are preferred for dynamic applications due to their higher elongation, abrasion tolerance, and ability to withstand wire bending during helical forming, with typical annulus temperature capability up to ~90 °C. Film/laminate systems—such as XLPE with metallized or aluminum layers, or multilayer stacks incorporating EVOH or PVDF—provide enhanced diffusion‑barrier performance for aggressive CO₂, H₂S, and moisture ingress scenarios, and may be selected where ultra‑low permeability is required. Dual‑layer structures, such as FBE primer combined with a PA11 topcoat, offer a balance of chemical resistance, adhesion, and flexibility suitable for mixed static‑dynamic service. Nanoclay‑reinforced polyamides further reduce permeability and improve resistance to crack propagation under cyclic loading. Metallic‑polymer hybrid coatings, for example Zn‑Al thermal spray underlayers with polymer overcoats, provide sacrificial galvanic protection in combination with barrier performance. Together, these coating systems broaden the design space by addressing performance, lifecycle, and cost constraints where environmental control, material substitution, or uncoated steel solutions are insufficient.
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This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
"Coating of Metallic Wires to Prevent Corrosion and Enhance Chemical and Mechanical Performance", Technical Disclosure Commons, (February 03, 2026)
https://www.tdcommons.org/dpubs_series/9269