316L Stainless Steel & Titanium Coil Tube for Hydrogen Electrolyzer Cooling Systems

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 132) offers a high-performance coil tube solution specifically engineered for hydrogen electrolyzer cooling applications in the new energy sector. These precision-wound coil tubes serve as critical thermal management components within both Alkaline (KOH) and Proton Exchange Membrane (PEM) electrolysis systems, where they operate under demanding conditions of 60–90 °C (140–194 °F) electrolyte temperatures in the presence of high-purity hydrogen gas (≥99.99 %).

Unlike conventional industrial coil tubes, these products are designed to address the dual challenges of aggressive alkaline corrosion and hydrogen permeation — the two primary degradation mechanisms encountered in hydrogen electrolysis environments. By combining superior metallurgical quality with specialized surface treatments, Wenzhou Jixing delivers coil tubes that maintain structural integrity and dimensional stability throughout extended operational lifetimes.

Material & Properties

316L Grade Stainless Steel

316L austenitic stainless steel is the primary material of choice for KOH-based alkaline electrolyzer cooling coils. The low-carbon variant (≤0.03 % C) minimizes intergranular corrosion susceptibility during welding and heat treatment processes. The addition of 2.0–3.0 % molybdenum provides exceptional resistance to chloride-induced pitting and crevice corrosion within the highly alkaline electrolyte environment (typically 25–30 wt% KOH at elevated temperatures).

Titanium (Grade 2 / Grade 5) Option

For PEM electrolyzer applications where hydrogen permeation through the cooling coil walls poses a critical contamination risk, titanium tubes (ASTM B348 Gr. 2 or Gr. 5 Ti-6Al-4V) are recommended. Titanium exhibits virtually zero hydrogen solubility and exceptional resistance to both acidic and alkaline environments, making it the gold-standard material for high-purity hydrogen systems.

Specifications

Parameter Specification
Material Grade ASTM A270 316L / ASTM B348 Titanium Gr. 2 or Gr. 5
Outer Diameter (OD) Φ6.00 – Φ38.00 mm (Φ0.236 – Φ1.496 in)
Wall Thickness 0.50 – 3.00 mm (0.020 – 0.118 in)
Bend Radius (R) ≥ 3D (3 × outer diameter), custom available
Coil Winding Diameter Φ100 – Φ2000 mm (Φ3.94 – Φ78.74 in)
Maximum Length per Coil Up to 500 m (1,640 ft), customizable
Operating Temperature 60 – 90 °C (140 – 194 °F) — electrolyte side
Maximum Operating Pressure Up to 3.0 MPa (435 psi)
Surface Finish Ra ≤ 0.4 μm (16 μin) — electrolyte-wetted side
Hydrogen Purity Compatibility ≥ 99.99 % H₂ (high-purity)
Electrolyte Compatibility 25–30 wt% KOH (Alkaline) / PEM acidic media
End Treatment Plain cut, beveled, or threaded — per customer specification
Standard Length Tolerance ± 0.5 %
Diameter Tolerance ± 0.05 mm (± 0.002 in)

Manufacturing Process

Step 1 — Raw Material Selection & Certification

Only certified mill-quality 316L austenitic stainless steel seamless tubing or ASTM-grade titanium pipe is accepted. Each batch undergoes full chemical composition analysis (OES spectroscopy) and mechanical property verification prior to processing.

Step 2 — Straightening & Annealing

Incoming tubes are cold-straightened to ensure axial straightness within 0.5 mm/m (0.005 in/ft). A solution annealing cycle at 1050–1100 °C (1922–2012 °F) in protective atmosphere restores full austenitic microstructure and eliminates residual stresses.

Step 3 — Precision Coiling / Bending

State-of-the-art CNC spiral coiling machines with mandrel support produce uniform coil tubes with controlled bend radii. The mandrel-insertion bending process prevents ovalization, ensuring dimensional accuracy of ≤ 2 % deviation from nominal OD after forming.

Step 4 — Post-Coil Annealing & Pickling

Coiled tubes undergo a controlled post-form annealing at 850–900 °C (1562–1652 °F) to relieve bending-induced residual stresses. Subsequent acid pickling and passivation (citric acid-based for 316L; hydrogen fluoride–nitric acid blend for titanium) removes surface oxides and establishes a protective passive film.

Step 5 — Internal Cleaning & Surface Treatment

The internal bore is cleaned using ultrasonic or high-pressure deionized water flushing to achieve an internal surface roughness of Ra ≤ 0.4 μm. For titanium options, a specialized hydrogen-removal anneal is performed to ensure zero dissolved hydrogen content.

Step 6 — Non-Destructive Testing & Quality Inspection

Every coil tube undergoes 100 % visual inspection, hydrostatic pressure testing at 1.5× working pressure, and dimensional verification. Spot checks include eddy current testing (ECT) for wall-thickness uniformity and helium leak detection for permeation integrity.

Applications

Alkaline (KOH) Hydrogen Electrolyzer Cooling

In alkaline water electrolysis systems operating at 60–90 °C with 25–30 wt% KOH electrolyte, these coil tubes serve as cooling heat exchangers within the electrolyzer stack. They remove excess heat generated by ohmic losses, maintaining optimal cell temperature for maximum Faradaic efficiency and membrane longevity.

PEM Electrolyzer Thermal Management

For Proton Exchange Membrane electrolyzers, titanium coil tubes are employed in the cooling circuit adjacent to the membrane electrode assembly (MEA). The titanium construction eliminates hydrogen permeation into the cooling loop, preserving the ≥99.99 % purity of the produced hydrogen gas.

Hydrogen Production Ancillary Systems

Quality Certifications & Standards Compliance

Unique Selling Points

Dual-Environment Engineering: Unlike standard industrial coil tubes, Wenzhou Jixing's electrolyzer-grade products are specifically engineered to simultaneously resist aggressive alkaline corrosion (KOH at 60–90 °C) and minimize hydrogen permeation — two failure modes that conventional materials cannot address concurrently.