CuNiFer Brake Line Coil | Cu90Ni6Fe4 Seamless Brake Tube Coil Manufacturer

Product Overview

What is CuNiFer Brake Line Tubing?

700+

Bar Burst Pressure (4.75mm OD)

30+

Year Corrosion-Free Service Life

5×

More Corrosion Resistant vs Bundy Steel

3D

Minimum Bend Radius Without Cracking

CuNiFer (Copper-Nickel-Iron) brake line tube is the premier material for hydraulic brake and fuel line applications in automotive, commercial vehicle, and off-highway equipment. The alloy — nominally 90% Copper, 6% Nickel, and 4% Iron (Fe) with trace manganese — was developed specifically to overcome the severe corrosion limitations of traditional Bundy (steel) brake tubing, particularly in road-salt environments.

Supplied as precision seamless tube coils in standard lengths of 25, 50, and 100 metres, CuNiFer brake line tubing is pre-coated with a polymer protective layer in many OEM applications, and can be bent, flared, and double-flared on-site using standard automotive tooling. It is approved by all major automotive OEMs and is the material of choice for European and North American vehicle manufacturers.

Exceptional Salt Corrosion Resistance

Resists road salt, calcium chloride, and moisture far superior to Bundy steel — the primary cause of brake line failure in cold-climate regions.

Excellent Formability & Flarability

Cold-bends without cracking to 3× OD radius; produces consistent ISO, SAE, and DIN double-flares without splitting — essential for leak-free fittings.

High Burst Pressure Safety Factor

Burst pressures exceeding 700 bar for standard 4.75 mm OD tube — providing a safety factor of 4× or greater versus typical braking system operating pressures of 150–180 bar.

OEM-Approved Automotive Material

Approved by BMW, Mercedes-Benz, Volvo, Scania, DAF, and other major OEMs. Compliant with DIN 74234, ISO 4038, and SAE J1047 brake tube standards.

Chemical Composition

CuNiFer Alloy Chemistry

The nominal Cu90/Ni6/Fe4 composition is optimised for automotive brake line service — balancing corrosion resistance, strength, and formability. Controlled per ISO 4038 and DIN 74234 material specifications.

Cu

Copper

Balance (~88%)

Ni

Nickel

5.0 – 7.0%

Fe

Iron

3.5 – 5.5%

Mn

Manganese

0.3 – 0.8%

Pb

Lead (max)

≤ 0.02%

Element	Symbol	Min (%)	Max (%)	Role in Braking System Performance
Copper	Cu	Balance	Balance	Matrix — provides excellent formability, conductivity, and corrosion base in wet environments
Nickel	Ni	5.0	7.0	Primary corrosion resistance element — forms stable protective oxide film; resists road salt attack
Iron	Fe	3.5	5.5	Critical for erosion-corrosion resistance under high-velocity hydraulic fluid flow; strengthens matrix
Manganese	Mn	0.3	0.8	Deoxidiser; improves hot workability and tube drawing performance; scavenges sulphur
Lead	Pb	—	0.02	Controlled impurity; low levels required for automotive RoHS and ELV (End of Life Vehicle) compliance
Zinc	Zn	—	0.30	Trace impurity limit
Carbon	C	—	0.05	Trace impurity limit
Sulphur	S	—	0.02	Trace impurity limit

* Composition per ISO 4038 Table 1 / DIN 74234. RoHS 2 (2011/65/EU) and ELV Directive (2000/53/EC) compliant — lead below threshold. All values weight percent.

Dimensional Standards & Size Charts

CuNiFer Brake Tube — Sizes & Specifications

Standard brake line tube sizes follow ISO 4038, DIN 74234, and SAE J1047. All dimensions in millimetres unless stated. Custom ODs and wall thicknesses available on request for OEM projects.

Standard Brake Tube Sizes — ISO 4038 / DIN 74234 ISO 4038DIN 74234

OD (mm)	OD (inch)	Wall Thickness (mm)	ID (mm)	Flow Area (mm²)	Weight (kg/m)	Primary Application
3.18	1/8"	0.71	1.76	2.43	0.053	Instrument & sensor lines
4.00	—	0.71	2.58	5.23	0.068	Small bore metric lines
4.75	3/16"	0.71	3.33	8.71	0.082	Standard passenger car brake lines (most common)
4.75	3/16"	0.89	2.97	6.93	0.099	Heavy duty / high-pressure passenger car
6.00	—	0.71	4.58	16.48	0.105	Larger passenger & light commercial vehicles
6.00	—	1.00	4.00	12.57	0.142	Heavy duty light commercial
6.35	1/4"	0.71	4.93	19.07	0.111	Light truck & SUV brake mains
6.35	1/4"	1.00	4.35	14.86	0.151	Heavy duty light truck
8.00	5/16"	1.00	6.00	28.27	0.194	HGV / truck brake mains & chassis lines
8.00	5/16"	1.25	5.50	23.76	0.237	Heavy truck high-pressure circuits
10.00	3/8"	1.00	8.00	50.27	0.246	Large HGV and bus brake main supply lines
10.00	3/8"	1.50	7.00	38.48	0.355	Off-highway high-pressure braking
12.00	—	1.00	10.00	78.54	0.298	Agricultural & construction equipment
12.70	1/2"	1.25	10.20	81.71	0.388	Heavy off-highway brake supply

Density of CuNiFer: 8.9 g/cm³. OD tolerance: ±0.05 mm. WT tolerance: ±0.04 mm per ISO 4038. Most common automotive size is 4.75 mm OD × 0.71 mm WT.

SAE vs ISO vs DIN Equivalent Sizes Cross-Reference

SAE Size	SAE OD (inch)	OD (mm)	WT (mm)	ISO 4038 Ref.	DIN 74234 Ref.	Thread / Fitting Type
—	—	4.75	0.71	Series A	Type A	M10×1 / ISO 7 Banjo
3/16"	0.1875"	4.76	0.028" (0.71)	Series A	Type A	3/16" SAE double flare
1/4"	0.250"	6.35	0.028" (0.71)	Series B	Type B	7/16"-24 UNF / M12×1
5/16"	0.3125"	7.94	0.028" (0.71)	Series C	—	1/2"-20 UNF
3/8"	0.375"	9.53	0.035" (0.89)	Series D	Type D	9/16"-18 UNF / M14×1.5

Standard Coil Supply Format

25 / 50 / 100 m

Standard Coil Lengths

200 – 350 mm

Coil Inner Diameter (ID)

Straight / Pre-coiled

Supply Options

Nylon / Bare / Lacquer

Coating Options

Capped / Sealed

End Condition (contamination-free)

MTR + CoC Included

Documentation with Each Coil

Mechanical Properties

Physical & Mechanical Data — CuNiFer Brake Tube

380

MPa (min)

Tensile Strength

Cold drawn condition per ISO 4038

275

MPa (min)

Yield Strength (0.2%)

Cold drawn, ISO 4038

25

% (min)

Elongation

On 50 mm gauge length

8.9

g/cm³

Density

At 20°C

40

W/m·K

Thermal Conductivity

At 20°C

3×

OD min

Minimum Bend Radius

Cold bend without cracking

Complete Physical Properties — CuNiFer vs Brake Fluid Compatibility

Property	Value	Unit	Condition / Notes
Density	8.9	g/cm³	At 20°C
Melting Range	1100 – 1150	°C	Liquidus to solidus
Tensile Strength (min)	380	MPa	Cold drawn, ISO 4038 / DIN 74234
Yield Strength 0.2% (min)	275	MPa	Cold drawn condition
Elongation (min)	25	%	50 mm gauge; required for double-flare forming
Vickers Hardness (HV)	120 – 165	HV	Cold drawn; within flarability range
Elastic Modulus	125	GPa	At room temperature
Thermal Conductivity	~40	W/m·K	At 20°C
Thermal Expansion Coeff.	17.0	×10⁻⁶/°C	Mean 20–300°C
Min Bend Radius	3 × OD	—	Cold bend, no mandrel; 2.5× with mandrel
Compatibility — DOT 3 Fluid	Fully Compatible	—	No swelling, no corrosion, no contamination
Compatibility — DOT 4 Fluid	Fully Compatible	—	Standard automotive brake fluid
Compatibility — DOT 5 (silicone)	Fully Compatible	—	Racing and military applications
Compatibility — Mineral Oil (LHM)	Fully Compatible	—	Citroën/Rolls-Royce hydraulic systems
Max Continuous Operating Temp.	150	°C	In brake fluid service; above caliper area
Min Operating Temp.	−55	°C	No embrittlement at sub-zero temperatures
RoHS / ELV Compliance	Yes	—	Pb <0.01%; meets 2000/53/EC and 2011/65/EU

Pressure & Burst Ratings

Hydraulic Burst & Working Pressure — CuNiFer Brake Tube

Calculated per ISO 4038 and DIN 74234. Burst pressure is the minimum hydraulic pressure at which the tube fails; working pressure applies a safety factor of 4. Standard automotive braking systems operate at 100–180 bar peak.

Burst Pressure & Allowable Working Pressure by Size ISO 4038

OD (mm)	WT (mm)	ID (mm)	Min Burst Pressure (bar)	Safety Factor	Allow. Working Press. (bar)	Typical System Press. (bar)	Safety Margin
4.75	0.71	3.33	700	4×	175	150–180	~4.0×
4.75	0.89	2.97	880	4×	220	150–180	~5.0×
6.00	0.71	4.58	548	4×	137	100–150	~4.5×
6.00	1.00	4.00	773	4×	193	100–150	~6.0×
6.35	0.71	4.93	516	4×	129	100–150	~4.3×
6.35	1.00	4.35	729	4×	182	100–150	~5.8×
8.00	1.00	6.00	575	4×	144	80–120	~5.5×
8.00	1.25	5.50	720	4×	180	80–120	~7.0×
10.00	1.00	8.00	460	4×	115	60–100	~5.0×
10.00	1.50	7.00	690	4×	173	60–100	~8.0×
12.70	1.25	10.20	480	4×	120	60–80	~7.0×

Burst pressure formula: P = (2 × S × WT) / OD where S = tensile strength (MPa). Min burst per ISO 4038: 700 bar for 4.75×0.71 mm. All pressure values in bar (1 bar = 14.5 psi = 0.1 MPa).

Brake System Operating Pressures (Reference)

Normal braking (passenger car)40 – 80 bar

Emergency / ABS braking100 – 180 bar

Race / performance brakingUp to 250 bar

HGV air-over-hydraulic systems80 – 120 bar

ABS pump pressure surgeUp to 200 bar (peak)

Min safety factor required (ISO)4.0 × (CuNiFer exceeds)

Pressure Test Requirements per Standard

ISO 4038 — Proof test pressure350 bar (30 sec hold)

ISO 4038 — Burst test pressure700 bar (min, 4.75mm)

DIN 74234 — Hydraulic test2 × working pressure

SAE J1047 — Pressure impulse50,000 cycles at 200 bar

Salt spray test (ISO 9227)500 hours (no red rust)

Flare leak testZero leakage at 500 bar

Material Comparison

CuNiFer vs Other Brake Line Materials

Understanding why CuNiFer is the preferred choice over Bundy steel, stainless steel, and nylon/polymer brake lines for OEM and replacement applications.

Recommended

CuNiFer

Cu90/Ni6/Fe4 — This product

Corrosion ResistanceExcellent

Salt Spray (hrs)500+ hrs

Burst Pressure700+ bar

FormabilityExcellent

Double FlarableYes

WeldableYes

RoHS / ELVCompliant

Weight vs SteelSame (8.9 g/cc)

Relative CostMedium

OEM ApprovalUniversal

Bundy (Steel) Tube

Zinc-coated steel — legacy

Corrosion ResistancePoor

Salt Spray (hrs)<96 hrs

Burst Pressure600+ bar

FormabilityGood

Double FlarableYes

WeldableYes

RoHS / ELVZinc issues

Weight vs SteelBaseline

Relative CostLow

OEM ApprovalBeing phased out

Stainless Steel (SS316)

High-grade alternative

Corrosion ResistanceVery Good

Salt Spray (hrs)1000+ hrs

Burst Pressure1000+ bar

FormabilityPoor

Double FlarableDifficult

WeldableYes (TIG only)

RoHS / ELVCompliant

Weight vs SteelSimilar

Relative CostHigh

OEM ApprovalMotorsport/Specialist

Nylon / Polymer Tube

Flexible hose alternative

Corrosion ResistanceExcellent

Salt Spray (hrs)N/A (no corrosion)

Burst Pressure200–400 bar

FormabilityExcellent

Double FlarableNo

WeldableNo

RoHS / ELVCompliant

Weight vs SteelMuch lighter

Relative CostLow–Medium

OEM ApprovalFuel lines only

Corrosion Performance — Salt Spray Test Comparison (ISO 9227) ISO 9227

Material	Salt Spray Hours (no red rust)	Condition After 500 hrs	Typical Field Life (salt-belt roads)	Failure Mode
CuNiFer (bare)	> 500 hrs	Light surface tarnish only; no corrosion	25 – 40 years	Physical damage only
CuNiFer (nylon coated)	> 1000 hrs	No change; coating intact	35+ years	Coating abrasion
Bundy steel (bare)	< 24 hrs	Heavy red rust; structural loss	3 – 8 years	Perforation corrosion
Bundy steel (galvanised)	48 – 96 hrs	Red rust through coating	5 – 12 years	Pitting under coating
Stainless steel SS316	> 1000 hrs	No corrosion	50+ years	Fatigue / fitting failure
Nylon PA12	N/A (non-metallic)	No corrosion	15 – 25 years	UV degradation / cracking

Complete Installation Guide

CuNiFer Brake Line — Cutting, Bending, Flaring & Installation Guide

A complete step-by-step technical guide for automotive technicians, fleet maintenance engineers, and OEM assembly personnel working with CuNiFer brake tube coils.

Step 1 — Measuring & Cutting

Measure twice: Route the tube before cutting; allow 10–15% extra for bends
Use a tube cutter: Rotary pipe cutter (not a hacksaw) for clean, square ends — essential for proper flare formation
Deburr completely: Remove all internal and external burrs with a reamer after cutting; burrs cause flare splitting and fluid leaks
Check squareness: End must be perpendicular to tube axis (±1°) before flaring
Clean the cut: Wipe with clean lint-free cloth; no contamination in the brake circuit
Avoid power tools: Angle grinders create heat and work-harden the cut end; always use rotary cutters

Step 2 — Bending Techniques

Minimum cold bend radius: 3 × OD (e.g., 14.25 mm min for 4.75 mm tube)
Use a tube bender: Rotary or lever-type bender sized to tube OD — mandatory for consistent bends
Never sharp-bend by hand: Causes kinking and wall thinning — weakens the tube fatally
Avoid wrinkles: Any wrinkle in the bend radius indicates over-bending or wrong tool size
Maintain roundness: Check OD ovality after bending — max 10% ovality allowed
Sequence: Slide nut and olive BEFORE bending — impossible to fit after
Tight-radius bends: Use a mandrel bender for bends tighter than 4 × OD
CuNiFer advantage: Stays bent — no spring-back like stainless steel

Step 3 — Flaring (ISO/DIN Double Flare)

Standard flare type: ISO/DIN double flare (also called a roll flare) — mandatory for brake systems per ECE R13
SAE flare: 45° single or double flare per SAE J533 — used in North American vehicles
Flare tool: Use a dedicated CuNiFer / soft-tube flare kit; never use tools sized for steel only
Clamp firmly: Tube must project correct distance from clamp face (varies by OD — see tool chart)
Two-stroke process: First stroke forms the initial dome; second stroke folds it into the double flare
Inspect the flare: Must be uniform, crack-free, and parallel to seat face; any split = scrap the tube
Lubricate: Apply clean brake fluid to flare seat before assembly — never grease
Do not over-torque: CuNiFer flares crush at correct torque — follow manufacturer's torque spec

Torque Specifications — Flare Nuts

3.18 mm OD (M8×1): 10 – 12 Nm
4.75 mm OD (M10×1): 14 – 17 Nm
4.75 mm OD (3/16" SAE): 11 – 14 Nm (97 – 124 in·lb)
6.35 mm OD (M12×1): 20 – 25 Nm
6.35 mm OD (1/4" SAE): 16 – 20 Nm
8.00 mm OD (M14×1.5): 28 – 32 Nm
10.00 mm OD (M16×1.5): 35 – 40 Nm
Critical: Never re-use old flare nuts — replace any disturbed fitting
Tighten sequence: Hand-tight first, then 1/6 turn (60°) additional with flare nut wrench

Routing, Clamping & Chassis Installation

Clamp spacing: Max 500 mm between clamps on chassis; 300 mm near flexible hose connections
Clamp type: Use plastic-lined P-clips or rubber-cushioned clamps — bare metal clips cause fretting
Avoid heat sources: Keep 50 mm minimum clearance from exhaust, catalytic converter, and hot surfaces
Avoid sharp edges: Route away from exposed metalwork; use grommets where passing through bulkheads
Protect from abrasion: Fit split-loom or nylon sleeve on sections exposed to road debris
Flexible hose connection: Allow 20 mm straight section before and after flexible hose to prevent flare stress
Loop at axle: Provide a 150 mm diameter loop near axle articulation points to prevent fatigue cracking
Downhill gradient: Route brake lines to drain moisture — avoid U-traps where water pools

Testing, Bleeding & Quality Checks

Visual inspection: Check all flares, bends, and clamps before pressurising system
Pressure test: Hold at 1.5× maximum system pressure for 5 minutes; inspect all joints
Bleed sequence: Follow OEM bleeding sequence; flush old DOT fluid completely before refilling
Leak check: Apply clean brake fluid around all fittings after bleeding; zero leakage acceptable
Pedal feel: Hard pedal (no sponginess) indicates properly bled, leak-free system
Road test: Test at low speed (10 km/h) with ABS activation before normal use
Documentation: Record tube sizes, batch number from MTR, and installation date for traceability
Regulatory: In commercial vehicles, brake system inspection forms part of mandatory vehicle certification (MoT / VOSA / TÜV)

Corrosion Protection & Maintenance

CuNiFer (bare): No additional coating required for standard automotive service
Nylon-coated option: Recommended for underbody routing in severe salt-belt regions (Northern Europe, Canada, US Rust Belt)
Wax injection: Apply cavity wax to body sections adjacent to brake lines for additional chassis protection
Inspect annually: Check for abrasion, kinking, or fitting seepage during annual service
No painting: Do not paint CuNiFer brake lines — paint traps moisture under the film
Glycol contamination: If coolant contacts brake tube exterior, flush area and inspect for pitting (unlikely but check)
Replacement trigger: Any visible physical damage, crimping, or fitting weeping — replace the complete affected section

Applicable Regulations & Certifications

ECE R13: UN Regulation on Braking of M, N & O Category Vehicles — mandates brake tube burst pressure >700 bar for passenger cars
ECE R13H: Passenger car specific braking regulation — CuNiFer meets all tube material requirements
2000/53/EC (ELV Directive): End-of-Life Vehicle — CuNiFer is fully recyclable; Pb < 0.01%
2011/65/EU (RoHS 2): Restriction of Hazardous Substances — CuNiFer compliant
ISO 9001:2015: Sunflex Metalloy quality management certification covering CuNiFer tube manufacture
IATF 16949: Automotive quality management — supply chain audit available on request
REACH (EU 1907/2006): No SVHC substances at concentrations above threshold

Coil Format & Packaging

Supply Format, Marking & Packaging

Coil Specifications

Coil inner diameter

200 mm – 350 mm (OD dependent)

Standard lengths

25 m, 50 m, 100 m per coil

Custom lengths

Available on request (min order applies)

Straightened lengths

Up to 6 m straight bars available

End condition

Both ends capped (plastic plug) — contamination-free

Coating options

Bare / Nylon PA12 coated / Lacquer coated

Internal cleanliness

Oil-free bore; particle count per ISO 16232

Packaging & Marking

Outer packaging

Polythene-wrapped coil in cardboard carton or wooden case

Coil wrapping

Tied with plastic straps at 3 points; no metal banding (prevents marking)

Label content

OD × WT, alloy grade, heat number, length, standard, net weight

Tube marking

Ink-jet or embossed: Grade / OD / WT / Standard / Heat No. / Manufacturer

Documentation

MTR (Mill Test Report) + CoC (Certificate of Conformance) per EN 10204 3.1

Traceability

Full heat traceability from raw material to finished coil

Export packing

Vacuum-sealed moisture-barrier bags in fumigation-free wooden crates

Applications

Where CuNiFer Brake Line Coils Are Used

Passenger Cars & SUVs

OEM and replacement brake line coils for all passenger vehicle classes. 4.75 mm OD the most specified size for modern cars from compact hatchbacks to luxury sedans.

HGV Trucks & Buses

Main brake line supply coils (8–10 mm OD) for heavy goods vehicles, coaches, and articulated lorries where brake line longevity is critical to fleet economics.

Light Commercial Vehicles

Vans, pick-ups, and LCV brake circuits — particularly high-value fleet vehicles where extended service intervals justify premium CuNiFer tubing over Bundy steel.

Off-Highway Equipment

Construction machinery, mining trucks, and agricultural tractors where brake systems face aggressive mud, chemical, and moisture environments requiring maximum corrosion life.

Military & Defence Vehicles

Armoured personnel carriers, military trucks, and defence fleet vehicles specifying CuNiFer for its proven longevity under demanding field conditions.

Aftermarket & Restoration

Classic car restoration, fleet brake line replacement, and automotive aftermarket — CuNiFer is the premium material of choice for comprehensive brake line replacement kits.

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