Insulating Gasket & Plastic Clip — Dissimilar Metal Isolation System for Stainless Steel Coil Tubes

1. Product Overview

The Insulating Gasket and Plastic Clip system is a critical engineering component designed for the installation and maintenance of stainless steel coil tubes (Coiltube). Its primary function is to establish a complete electrical isolation barrier between stainless steel tubing and carbon steel support brackets or hangers, thereby preventing galvanic corrosion (Bimetallic Corrosion) that arises from the contact of dissimilar metals in the presence of an electrolyte.

When stainless steel (such as grades 304, 316, or 316L) is brought into direct contact with carbon steel (mild steel, structural steel) in environments where rainwater, atmospheric moisture, or condensation (Condensate) is present, a galvanic cell is formed. The potential difference between the noble stainless steel and the active carbon steel, combined with the conductive electrolyte, drives rapid electrochemical dissolution of the carbon steel component. Under severe conditions — particularly in coastal, industrial, or high-humidity environments — the galvanic corrosion rate can exceed 100 times the normal atmospheric corrosion rate, leading to structural failure of supports, leakage, and premature system degradation.

This product line, manufactured by Wenzhou Jixing Metal Materials Co., Ltd, provides a reliable, durable, and code-compliant solution for dissimilar metal isolation in piping and tube support systems.

2. Material & Properties

Insulating gaskets and plastic clips are engineered from high-performance polymer materials selected for their exceptional electrical resistivity, mechanical strength, chemical resistance, and dimensional stability across a wide temperature range.

Primary Material Options:
- PTFE (Polytetrafluoroethylene): Superior chemical inertness, coefficient of friction as low as 0.04, operating temperature range of −260 °C to +260 °C, electrical resistivity exceeding 10¹⁸ Ω·cm.
- Polyethylene (HDPE/UHMWPE): High impact resistance, excellent moisture resistance, electrical resistivity >10¹⁶ Ω·cm, cost-effective for moderate-temperature applications.
- Phenolic Resin Composites: Enhanced thermal resistance up to 150 °C continuous, high compressive strength, suitable for high-load support applications.
- Nylon (Polyamide 6/66): Balanced mechanical properties, good fatigue resistance, suitable for clip and clamp configurations.
Key Performance Characteristics:
- Volume Resistivity: ≥10¹⁵ Ω·cm (ensuring complete galvanic isolation)
- Compressive Strength: 5–60 MPa (depending on material grade)
- Thermal Conductivity: 0.15–0.25 W/(m·K) (provides secondary thermal insulation benefit)
- UV Resistance: Stabilized formulations available for outdoor exposure
- Chemical Resistance: Inert to acids, alkalis, salts, and industrial solvents

3. Specifications

Parameter	Specification	Notes
Product Category	Insulating Gasket / Plastic Clip	Dissimilar Metal Isolation
Application Level	Installation & Maintenance — Protective Measures	Level 3 Subdivision: Dissimilar Metal Isolation
Compatible Tube Material	Stainless Steel (304, 316, 316L, 321, 347, Duplex 2205)	Coiltube / Coil Tube configurations
Compatible Support Material	Carbon Steel (Q235, A36, ASTM A36, Structural Steel)	Brackets, hangers, saddles
Electrical Resistivity	≥10¹⁵ Ω·cm	Ensures galvanic isolation integrity
Operating Temperature	−40 °C to +250 °C (PTFE); −40 °C to +120 °C (Nylon/PE)	Select grade per service conditions
Compressive Load Capacity	Up to 50 kN per gasket (phenolic); Up to 20 kN (polymer)	Verify per specific dimension
Thickness Range (Gasket)	2 mm – 12 mm	Custom thickness available
Clip Diameter Range	Φ6 mm – Φ325 mm	Matches coil tube OD
Standard Compliance	ASTM B165, ISO 10434, EN 10216, NACE SP0169	Galvanic corrosion prevention standards
Surface Treatment	Smooth, UV-stabilized, anti-aging	Low-friction finish for tube compatibility
Service Life	≥25 years (outdoor); ≥40 years (indoor)	Under specified environmental conditions
Manufacturer	Wenzhou Jixing Metal Materials Co., Ltd	Product No. 222

4. Manufacturing Process

The production of insulating gaskets and plastic clips follows a rigorous multi-stage manufacturing process to ensure consistent quality, dimensional accuracy, and material integrity:

Raw Material Selection & Verification: Virgin polymer resins (PTFE homopolymer, HDPE, Nylon 66, or phenolic composite) are sourced from certified suppliers. Each batch undergoes incoming inspection for molecular weight, melt flow index, and impurity content.
Mixing & Compounding: Functional additives — including UV stabilizers (HALS, benzotriazole), anti-oxidants, flame retardants (where required), and colorants — are blended with the base resin under controlled temperature and shear conditions.
Forming:
- Gaskets: Formed via compression molding (for phenolic) or hot-press cutting from pre-extruded sheets (for PTFE/PE). PTFE gaskets may also be produced by cold-press and sintering (Sintering Temperature: 360–400 °C).
- Clips: Produced via injection molding (Nylon, PE) or compression molding (PTFE). Precision tooling ensures consistent wall thickness and engagement geometry.
Post-Processing: Parts undergo stress-relief annealing (where applicable), dimensional trimming, and surface finishing to eliminate flash and ensure smooth contact surfaces.
Quality Control & Testing: Each production lot is subjected to:
- Electrical resistivity testing (per ASTM D257)
- Compressive strength verification (per ASTM D695)
- Dimensional inspection (CMM or calibrated gauges)
- Visual and surface defect inspection
- Aging and thermal cycling tests (accelerated life testing)
Packaging & Traceability: Finished products are packaged with protective wrapping, labeled with batch identification, material grade, and compliance documentation for full supply-chain traceability.

5. Applications

The Insulating Gasket and Plastic Clip system is indispensable in any application where stainless steel coil tubes are supported by carbon steel structures and exposed to moisture or electrolytic environments:

Chemical Processing Plants: Reactor cooling coils, heat exchanger tube bundles, and process piping supported by structural steel frames in environments with corrosive condensates.
Oil & Gas Industry: Separators, scrubbers, and offshore platform piping where saltwater spray and humidity accelerate galvanic corrosion.
Power Generation: Condenser tubes, feedwater systems, and steam turbine exhaust piping mounted on carbon steel frameworks.
Food & Pharmaceutical Processing: Sanitary stainless steel tubing systems requiring corrosion-free support isolation, with materials compliant with FDA and EHEDG standards.
Marine & Offshore Engineering: Coastal and subsea installations where continuous exposure to saltwater and condensation creates aggressive galvanic environments.
Building Services & HVAC: Condenser coils, chilled water piping, and ventilation duct supports where condensation is a persistent concern.
Aerospace & Defense: Fuel system tubing, hydraulic lines, and structural supports requiring guaranteed galvanic isolation under extreme environmental conditions.

6. Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and ensures all insulating isolation products conform to internationally recognized standards:

ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
ASTM B165 — Standard specification for non-metallic gaskets for flanged and other pressure-containing joints (material performance reference).
ASTM D257 — Standard test methods for DC resistance or conductance of insulating materials (electrical isolation verification).
ASTM D695 — Standard test method for compressive properties of rigid plastics (mechanical load verification).
NACE SP0169 — Recommended practice for cathodic protection of underwater or buried metallic structures (galvanic corrosion prevention framework).
ISO 10434 / EN 10216 — Standards for seamless stainless steel tubes (compatibility with supported tube specifications).
CE Marking — Conformity with European regulatory requirements for safety and environmental performance.
RoHS Compliance — Restriction of Hazardous Substances directive compliance for environmental safety.

7. Unique Selling Points

Eliminates Galvanic Corrosion: Provides a verified electrical isolation resistance exceeding 10¹⁵ Ω·cm, completely preventing the formation of a galvanic cell between stainless steel tubing and carbon steel supports, even under continuous rainwater or condensation exposure.
Engineered for Coil Tube Geometry: Specifically designed for the unique curvature and repetitive support requirements of coil tube (Coiltube) installations, ensuring uniform contact pressure and reliable isolation at every support point.
Multi-Material Platform: Available in PTFE, HDPE, Nylon, and phenolic composite grades to match the specific temperature, load, and chemical environment of each application.
Extended Asset Life: Prevents premature degradation of support structures and tube assemblies, reducing maintenance frequency and unplanned shutdown costs by up to 80% compared to unprotected installations.
Full Traceability & Compliance: Every product batch is accompanied by material test certificates, electrical resistivity reports, and dimensional inspection records, ensuring full supply-chain accountability.
Custom Fabrication Capability: Non-standard dimensions, thicknesses, and configurations are available to meet project-specific engineering requirements.

Engineering Note: Under rainwater or condensation conditions, the galvanic corrosion rate between stainless steel and carbon steel can reach 10–500 μm/year — orders of magnitude higher than normal atmospheric corrosion rates. This insulating isolation system is not optional; it is a mandatory engineering control for the long-term structural integrity and operational safety of stainless steel coil tube installations.