RFQ Today
Certifications: EN 10204 3.1 / material test certificates, RoHS / REACH compliance, anodising certification, and complete export documentation packages.
Aluminium
Tube &
Fittings
A world-class technical reference for EPC contractors, mechanical and process engineers, procurement heads, and global project buyers specifying aluminium tube, aluminium hydraulic and pneumatic fittings, aluminium manifold blocks, and aluminium fluid distribution components — covering alloy grade selection, temper classification, corrosion performance, pressure rating, joining methods, and the specific engineering considerations that distinguish aluminium from steel in fluid power, pneumatic, and instrument piping applications.
Alloy Classification
& Selection Principles
Aluminium tube and fittings are specified over steel wherever the weight–strength ratio, corrosion resistance in mild environments, thermal conductivity, machinability, or non-magnetic properties of aluminium provide a decisive engineering or operational advantage over steel alternatives.
1.1 — Engineering Context and Aluminium Advantages
Aluminium is the most widely used non-ferrous metal in fluid power and pneumatic system components. Its density of 2.70 g/cm³ — approximately one-third that of steel (7.85 g/cm³) — enables hydraulic manifolds, pneumatic cylinders, valve bodies, and distribution blocks to be manufactured at a fraction of the weight of equivalent steel components, with minimal reduction in structural integrity for the majority of industrial pressure applications. This weight advantage is the primary driver for aluminium specification in mobile hydraulics, aerospace fluid systems, vehicle pneumatics, food and beverage piping (aluminium passes FDA food-contact requirements without coatings), and any installation where reduced system weight translates to lower energy consumption, easier installation, or improved dynamic performance.
Aluminium forms a thin, adherent oxide layer (Al₂O₃) on its surface when exposed to air — the passive oxide provides inherent corrosion resistance in neutral and mild atmospheric environments without any applied coating. In dry compressed air, instrument air, and nitrogen service: aluminium tube and fittings provide equivalent or better corrosion resistance to zinc-plated carbon steel at lower weight and with superior appearance. However, aluminium has specific corrosion vulnerabilities: it is attacked by alkaline environments (pH > 9), concentrated acids (except concentrated H₂SO₄ and HNO₃ in which it is passive), mercury and mercury compounds (catastrophic corrosion), copper alloys in galvanic contact, seawater above 70°C, and chloride-containing fluids in stagnant or crevice conditions — the engineer must confirm the compatibility of aluminium with the specific fluid, environment, and galvanic contact situation before specifying aluminium tube or fittings.
1.2 — Aluminium Alloy Grade Classification for Tube and Fittings
6061 — General Purpose Structural and Pressure Alloy
The most widely used aluminium alloy for hydraulic fittings, manifold blocks, pneumatic cylinder bodies, and structural tube. 6061 is an Al-Mg-Si alloy (0.8–1.2% Mg, 0.4–0.8% Si) with excellent machinability (particularly in T6 temper), good weldability, and moderate-to-good corrosion resistance in atmospheric and fresh water environments. Typical properties in T6 temper: UTS 310 MPa; yield strength 275 MPa; elongation 12%; Brinell hardness 95 HB. Widely available as drawn tube (ASTM B210/B241), extruded rod and bar (ASTM B221), and plate (ASTM B209). The standard alloy for aluminium hydraulic manifold blocks, valve bodies, and DIN 24° / BSP hydraulic fittings in mobile and industrial hydraulic systems.
6063 — Architectural and Pneumatic Distribution Alloy
Al-Mg-Si alloy similar to 6061 but with lower Mg and Si content — optimised for surface finish and extrudability rather than maximum strength. 6063-T6 properties: UTS 215 MPa; yield strength 170 MPa; elongation 12%. Better surface finish than 6061 (used for architectural extrusions, anodised profiles) and better corrosion resistance in mild atmospheric service. Used for: aluminium pneumatic cylinder profiles (extruded with integrated rod bore and mounting grooves); aluminium pneumatic distribution rail profiles; and aluminium structural sections in food and beverage equipment where appearance and anodise quality are important. Not used for high-pressure hydraulic fittings — insufficient yield strength for most hydraulic pressure classes above 100 bar.
5083 — Marine and Weld-Critical Alloy
Al-Mg alloy (4.0–4.9% Mg) with the highest strength of the non-heat-treatable aluminium alloys. 5083-H111 / H321 properties: UTS 290–320 MPa; yield strength 145–230 MPa; elongation 16%. Excellent corrosion resistance in seawater and marine atmospheres — the Mg content provides cathodic protection against pitting corrosion in chloride environments. Cannot be heat-treated to increase strength (non-heat-treatable series). Used for: offshore platform aluminium piping (seawater cooling distribution, aluminium piping on FPSO topsides); shipbuilding aluminium pipework; and welded aluminium pressure vessels and tanks in marine service. Welding with ER5356 filler provides matching mechanical properties in the weld zone — critical for 5083 pressure applications.
2024 — High-Strength Aerospace Alloy
Al-Cu alloy (3.8–4.9% Cu) — the classic aerospace structural alloy. 2024-T3 properties: UTS 483 MPa; yield strength 345 MPa; elongation 18%. Highest strength-to-weight ratio of common aluminium alloys but with significantly lower corrosion resistance than 6061 or 5083 — the Cu content makes 2024 susceptible to pitting and intergranular corrosion in moist environments. Typically used with a cladding (Alclad 2024) or surface protection (anodise, chromate conversion coating) for all non-aerospace-controlled applications. Used for: aircraft hydraulic system fittings (SAE AS4395 / MS fittings); aerospace pneumatic system components; and high-strength structural fluid system brackets where 6061 strength is insufficient. Not used for uncoated outdoor or marine service.
7075 — Maximum-Strength Aerospace / Tooling Alloy
Al-Zn-Mg-Cu alloy — the highest-strength standard aluminium alloy. 7075-T651 properties: UTS 572 MPa; yield strength 503 MPa; elongation 11%. Used where absolute minimum weight is required with no compromise on strength: aircraft wing structures, aerospace hydraulic manifolds, high-performance racing vehicle components, and tooling blocks for high-pressure aluminium die casting. Very poor weld joint strength (significant HAZ softening) — 7075 hydraulic components are typically machined from billet, never welded. Stress corrosion cracking (SCC) susceptibility in T6 temper in marine and humid environments: specify T73 or T7351 over-aged temper for improved SCC resistance in service. Higher cost and limited tube availability vs 6061 — specify 7075 only where the strength margin over 6061 is necessary.
1050 / 1100 — Pure Aluminium Tube (Soft / Chemical)
Near-pure aluminium (1050: 99.5% Al; 1100: 99.0% Al) — very low strength (UTS 60–95 MPa) but maximum formability, ductility, and chemical resistance. Used for: soft bending aluminium tube in refrigeration and HVAC systems; aluminium chemical tubing where the process chemistry is incompatible with the alloying elements in 6061 or 5083; electrical bus bar applications; food-contact aluminium tubing (1050 is FDA-compliant for direct food contact without coatings); and decorative aluminium tube where easy bending and forming are required. Not suitable for pressure service above 10–15 bar without very heavy wall thickness — specify 6061 or 5083 for pressure-rated aluminium tube.
1.3 — Temper Classification for Aluminium Tube and Fittings
| Temper | Designation Meaning | Typical UTS (6061) | Typical Yield (6061) | Application Guidance |
|---|---|---|---|---|
| O (Annealed) | Fully annealed — maximum ductility | 125 MPa | 55 MPa | Bending, forming, deep drawing; not pressure service |
| T4 | Solution heat-treated, naturally aged | 240 MPa | 145 MPa | Formable with moderate strength; intermediate applications |
| T6 | Solution HT + artificial ageing (peak) | 310 MPa | 275 MPa | Standard for hydraulic fittings and pressure tube |
| T651 | T6 + stress-relieved by stretching | 310 MPa | 275 MPa | Plate and bar for manifold machining — reduced residual stress |
| T73 | Over-aged for SCC resistance (7xxx) | 505 MPa (7075) | 435 MPa (7075) | 7075 in marine / humid environment (improved SCC resistance) |
| H111 | Strain-hardened + partial anneal | 270 MPa (5083) | 145 MPa (5083) | 5083 tube and sheet in marine and welded structures |
| H321 | Strain-hardened, stabilised (5xxx) | 305 MPa (5083) | 215 MPa (5083) | 5083 plate for marine vessels and offshore structures |
1.4 — Pressure Rating and Burst Pressure Calculation
t = Wall thickness (mm)
σ_UTS = Ultimate tensile strength of alloy-temper combination (MPa) — see Table 1.A
OD = Outside diameter (mm)
SF = Safety factor — typically 4:1 for hydraulic tube (ISO 4413); 3:1 for structural
Key design note — Heat-Affected Zone (HAZ) softening:
Welding aluminium alloys in the T6 temper causes significant HAZ softening — the UTS in the HAZ drops to approximately the O-temper value (125 MPa for 6061 vs 310 MPa for T6 unwelded). Never use the T6 UTS value to calculate the pressure rating of a welded aluminium tube assembly — use the annealed / HAZ strength value for welded sections. For pressure-rated aluminium tube circuits: avoid welded connections; use compression fittings or flanged connections instead.
σ_UTS (6061-T6) = 310 MPa
P_burst = 2 × 2.0 × 310 / 12 = 1033 bar
Working pressure (SF = 4:1): WP = 1033 / 4 = 258 bar
For 200 bar hydraulic pilot line: 12 mm × 2.0 mm 6061-T6 is adequate with a 1.29× margin above WP.
Submit your OD, wall, alloy, temper, pressure rating, and quantity for a documented RFQ within 24 hours.
Pressure Ratings
& Standards Compliance
Aluminium tube dimensions, wall thicknesses, alloy designations, and temper conditions are governed by ASTM B210, B241, EN 573, EN 754, and ISO 6361. All applicable standards are supported at RR Hydraulic.
Submit OD, wall, alloy grade, temper, quantity, and application to sales@rrhydraulics.com for a certified offer.
2.1 — 6061-T6 Aluminium Tube Working Pressure Reference
| OD (mm) | Wall (mm) | ID (mm) | Burst Pressure (bar) | WP at SF 4:1 (bar) | Weight (kg/m) | Typical Application |
|---|---|---|---|---|---|---|
| 6 | 1.0 | 4.0 | 1,033 | 258 | 0.042 | Instrument; pilot line; small hydraulic |
| 8 | 1.0 | 6.0 | 775 | 194 | 0.057 | Pneumatic; instrument; pilot circuit |
| 8 | 1.5 | 5.0 | 1,163 | 291 | 0.082 | Hydraulic pilot; medium pressure |
| 10 | 1.5 | 7.0 | 930 | 233 | 0.104 | General hydraulic; pneumatic supply |
| 12 | 1.5 | 9.0 | 775 | 194 | 0.126 | Hydraulic distribution; pneumatic |
| 12 | 2.0 | 8.0 | 1,033 | 258 | 0.163 | Medium-pressure hydraulic circuits |
| 16 | 2.0 | 12.0 | 775 | 194 | 0.221 | Hydraulic return; compressed air |
| 20 | 2.5 | 15.0 | 775 | 194 | 0.346 | Hydraulic tank line; air distribution |
| 25 | 3.0 | 19.0 | 744 | 186 | 0.540 | Large hydraulic; pneumatic header |
2.2 — Applicable Standards and Compliance Framework
ASTM B210 / B241
ASTM B210: Aluminium and Aluminium-Alloy Drawn Seamless Tubes — governs the dimensions, tolerances, mechanical properties, and testing of cold-drawn seamless aluminium tube in alloys including 1100, 2024, 3003, 5052, 6061, 6063, and 7075. ASTM B241: Aluminium and Aluminium-Alloy Seamless Pipe and Seamless Extruded Tube — covers extruded (as opposed to cold-drawn) seamless aluminium tube, primarily for larger OD sizes. B210 is the primary standard for drawn precision tube for hydraulic and pneumatic fittings and instrument lines; B241 for larger structural tube and pipe. Both standards specify alloy and temper by UNS designation and Aluminium Association (AA) designation — always cite the specific alloy (e.g., 6061) and temper (e.g., T6) in procurement specifications.
EN 573 / EN 754 / ISO 6361
EN 573: Aluminium and Aluminium Alloys — Chemical Composition and Form of Wrought Products. The European standard defining alloy composition for EN-AW-6061 (equivalent to AA 6061), EN-AW-5083 (AA 5083), EN-AW-7075 (AA 7075), and all other standard European aluminium wrought alloys. EN 754: Aluminium and Aluminium Alloys — Cold Drawn Rod/Bar and Tube. Governs dimensions, tolerances, and mechanical properties of cold-drawn aluminium tube for European projects. ISO 6361: Wrought Aluminium and Aluminium Alloy Sheets, Strips, and Plates — the ISO dimensional standard. For European EPC projects: EN 573 / EN 754 are the governing standards; ASTM B210 alloys are accepted with appropriate EN-to-ASTM cross-reference on the material certificate.
ISO 4413 (Hydraulic Safety)
ISO 4413 Hydraulic fluid power — general rules and safety requirements — governs aluminium tube and fittings used in hydraulic circuits. ISO 4413 Section 5.4 covers tube and pipe materials: aluminium alloy tube is acceptable for hydraulic circuits provided the working pressure does not exceed the calculated allowable based on the tube OD, wall thickness, and alloy yield strength with the required safety factor (minimum 4:1 burst-to-working pressure). ISO 4413 also notes that aluminium tube must not be used with hydraulic fluids that attack aluminium — specifically: water-glycol HF-C type fire-resistant fluid (alkaline additives attack aluminium), phosphate ester HF-D type (attacks aluminium), and any fluid with pH > 9.0. Mineral oil, synthetic ester, and polyalkylene glycol (PAG) hydraulic fluids are generally compatible with aluminium.
SAE AS4395 / MS Fittings (Aerospace)
SAE AS4395 (Fittings, Tube, Flared, AN/MS) and the US Military Standard (MS) fitting series govern aluminium flared tube fittings for aerospace and defence hydraulic systems. AN (Army-Navy) and MS aluminium fittings are 2024-T4 or 6061-T6 alloy with 37° flared tube ends (same geometry as JIC 37° steel fittings but in aluminium). The aluminium AN/MS fitting system is the standard for military aircraft hydraulic circuits (Skydrol phosphate ester resistant — aluminium is attacked by Skydrol; verify AS4395 fitting compatibility with Skydrol before use). For commercial aviation and aerospace EPC: AS4395 aluminium fittings with aluminium alloy tube are the standard lightweight hydraulic circuit components where weight reduction is the overriding design driver.
ISO 8434-1 (DIN 24° Aluminium)
ISO 8434-1 DIN 24° bite-type fittings are available in aluminium alloy body (6061-T6 or similar) for low-to-medium pressure hydraulic circuits in mobile equipment and industrial machinery where weight reduction is a priority. Aluminium DIN 24° fittings are compatible with aluminium hydraulic tube (6061-T6) and are used with mineral oil hydraulic fluid. Key limitation: aluminium DIN 24° fittings have lower working pressure ratings than equivalent steel fittings at the same tube OD due to the lower yield strength of 6061-T6 vs carbon steel — verify working pressure rating vs system design pressure before specifying aluminium DIN fittings. Also: aluminium cutting rings (bite rings) must be used with aluminium tube in aluminium DIN fittings — steel cutting rings in aluminium fittings create a galvanic couple that corrodes the aluminium fitting body at the ring/fitting interface in humid service environments.
EU Drinking Water Regulations / FDA
Aluminium contact with drinking water is regulated in the European Union under the Council of Europe Resolution AP(2013)5 on metals and alloys used in contact with drinking water, and by individual national regulations (ACS in France, KTW in Germany, WRAS in the UK). Alloys 1050, 1100, 3003, and 6063 are generally accepted for potable water contact; 6061 with its higher Cu content (0.15–0.40%) requires verification against the applicable national drinking water regulation. For food-contact aluminium in the USA: FDA 21 CFR 175.300 covers aluminium resinous coatings on food-contact surfaces; uncoated aluminium (1xxx and 3xxx series) is generally recognised as safe (GRAS) for dry food contact. Always confirm the specific alloy’s compliance with the applicable food or drinking water contact regulation for the project country before ordering.
RoHS / REACH
Aluminium alloys are generally RoHS compliant — the restricted substances (lead, mercury, cadmium, chromium VI, PBB, PBDE, DEHP, DBP, BBP, DIBP) are not present in standard aluminium alloy compositions at restricted levels. Exception: some cutting fluids and machining aids used in aluminium fitting manufacture may contain restricted substances — demand the Declaration of Conformity from the fitting manufacturer for European EPC project supply where RoHS compliance of assembled components is a project contractual requirement. REACH: aluminium alloys do not contain SVHCs (substances of very high concern) in their base compositions but some surface treatment chemicals (hexavalent chromate conversion coatings — Cr(VI) per MIL-DTL-5541 Type I) are SVHCs under REACH — specify Cr(III) conversion coating (Alodine 1200S, Alocrom 1000) or anodising instead of Cr(VI) treatments for REACH-compliant European EPC projects.
EN 10204 / ASTM E8 (Material Certification)
EN 10204 3.1 material test certificates are required for aluminium tube and fittings on EPC projects — the same requirement as for steel fittings. The MTC must include: alloy designation (EN-AW-6061 or AA 6061); temper (T6, T651, H111, etc.); chemical analysis per EN 573-3 or ASTM B210 composition limits; mechanical properties (UTS, yield, elongation per ASTM E8 / EN ISO 6892-1 tensile test); and heat/lot number for traceability. EN 10204 3.2 (TPI countersign) for offshore, food-grade, and aerospace aluminium component supply. Hardness testing (Brinell per ISO 6506; Vickers per ISO 6507) on sampled lot as a quick indirect verification of the temper condition — T6 temper 6061 target hardness 90–100 HB.
Joining Methods
& Fabrication Controls
Aluminium surface treatment significantly extends service life in demanding environments. Joining aluminium requires method selection appropriate to the alloy, temper, and pressure service — welding, flaring, compression, and brazing each suit different aluminium tube applications. RR Hydraulic advises on the correct treatment and joining method for each application.
3.1 — Surface Treatment Options for Aluminium Tube and Fittings
Type II Sulphuric Acid Anodising (MIL-A-8625 Type II / ISO 7599)
The standard decorative and protective anodising process — forms a hard, porous aluminium oxide layer 5–25 µm thick on the aluminium surface. Type II anodising: improves corrosion resistance in atmospheric and humid environments (salt spray resistance 500–1000 hours per ISO 9227 in sealed condition); provides a hard surface (400–600 Vickers) that resists wear and abrasion better than bare aluminium; is electrically insulating (prevents galvanic contact corrosion at dissimilar metal interfaces); and accepts colour dyes for identification. Suitable for: pneumatic cylinder profiles; aluminium manifold block external surfaces; hydraulic fitting bodies in mild service; and all aluminium components requiring improved corrosion resistance without the thickness penalty of paint or plating. Not suitable for food-contact surfaces unless using food-grade anodising process (Type II with post-seal in hot DI water only — no chromate or dye sealers).
Type III Hard Anodising (MIL-A-8625 Type III)
High-voltage, low-temperature sulphuric acid anodising producing a thick, very hard oxide layer (25–75 µm, hardness 400–600 Vickers surface, up to 2000 Vickers at depth). Type III hard anodising dramatically improves: wear resistance (aluminium cylinder bores, valve spools, and sliding surfaces); corrosion resistance (salt spray >2000 hours in sealed condition); and dimensional stability of aluminium hydraulic components in high-cycle service. Used for: aluminium pneumatic and hydraulic cylinder bores (the piston seal runs on the hard-anodised bore — surface hardness replaces the need for a steel liner in moderate-pressure aluminium cylinders); aluminium hydraulic valve bodies; and aluminium manifold block fluid circuit bore surfaces in corrosive process environments. The hard anodise layer increases the bore dimension (grows inward approximately 50% of the layer thickness) — this must be accounted for in the pre-anodise machining tolerances.
Chromate Conversion Coating (Alodine / Alocrom)
Chemical conversion coating forming a thin (0.5–3 µm) chromate layer on the aluminium surface — provides: good corrosion resistance (400–600 hours salt spray per ISO 9227); electrically conductive surface (unlike anodising — critical for EMI/RF shielding in electronic enclosures and aerospace avionics boxes); good adhesion primer for paint and adhesive bonding; and low contact resistance for electrical grounding connections. Two types: Cr(VI) (MIL-DTL-5541 Type I — yellow/gold appearance, maximum corrosion resistance, REACH SVHC — restricted in EU) and Cr(III) (MIL-DTL-5541 Type II — clear/iridescent, lower corrosion resistance than Cr(VI), REACH compliant). For European EPC projects: specify Cr(III) Alodine 1200S or equivalent REACH-compliant conversion coating — Cr(VI) hexavalent chromate is an authorisation substance under REACH.
Electroless Nickel Plating (ENP) on Aluminium
Electroless nickel (8–25 µm, ASTM B733) on aluminium: provides corrosion resistance in chemical and marine environments where the bare aluminium would be attacked; improves surface hardness (550–650 Vickers for high-phosphorus ENP); and provides a solderable/brazeable surface for electronic assembly applications. ENP on aluminium requires a zincate pre-treatment (zinc immersion before nickel plating) to ensure adhesion to the aluminium surface. ENP aluminium fittings are used for: chemical plant instrument connections where both aluminium lightweight and chemical corrosion resistance are required; aluminium hydraulic fittings in marine service where seawater exposure would attack bare aluminium; and aluminium manifold blocks in chemical process equipment with aggressive fluid environments. Verify ENP adhesion per ASTM B571 bend test before project supply approval.
PTFE Coating / Fluoropolymer Lining
Spray-applied PTFE or fluoropolymer coating on aluminium internal bore surfaces — provides chemical resistance to process fluids that would attack bare aluminium (alkalis, acids, solvents) while retaining the lightweight aluminium structure for external mechanical loads. Used for: aluminium chemical process piping in pharmaceutical and food plants where aluminium tube provides weight advantage but the process fluid is mildly corrosive to bare aluminium; aluminium distribution manifolds in chemical dosing systems; and aluminium valve bodies where the internal bore must be chemically inert but the body must be lightweight. PTFE internal coating thickness: 25–75 µm — must be continuous with no pinholes for chemical containment service. Verify PTFE coating integrity by high-voltage spark test per ASTM D229 before process service.
Paint and Powder Coat
Wet paint (2-pack epoxy; polyurethane) or powder coat (epoxy-polyester, polyester, or TGIC polyester) over a chromate conversion or anodise primer — the most cost-effective corrosion protection for aluminium structures and large-area aluminium components in outdoor service. Powder coat provides 60–120 µm uniform coating with excellent impact and chip resistance. Used for: aluminium pneumatic cylinder mounting plates; aluminium distribution manifold external surfaces; aluminium tubing in outdoor installations where UV and weather protection is required; and aluminium hydraulic reservoirs in mobile equipment. For marine and offshore aluminium components: 2-pack epoxy paint over chromate primer provides the best paint system corrosion resistance — specify a full offshore paint system (chromate primer + epoxy intermediate + polyurethane topcoat) for aluminium components on offshore FPSO and platform topside exposure.
3.2 — Joining Methods for Aluminium Tube
- Compression fittings (ISO 8434-1 DIN 24°, Swagelok-type): The preferred joining method for aluminium tube in hydraulic and pneumatic circuits — compression fittings in aluminium body (6061-T6) with aluminium cutting ring (for aluminium tube) require no heat, no welding qualification, no post-weld heat treatment, and preserve the T6 temper strength of the tube. Working pressure limited by the aluminium fitting body strength, not the tube strength. Verify that the compression fitting body and cutting ring are both aluminium alloy — steel cutting rings in aluminium fittings create a galvanic couple at the bite ring contact zone
- Flare fittings (JIC 37° / AN 37°): Used in aerospace and military hydraulic circuits — the tube end is flared to 37° using a precision flaring tool, and the flared tube end seats against the 37° cone face of the aluminium fitting. No HAZ softening issue (no heat used); preserves T6 temper. Tube wall must be thick enough to withstand the flaring force without cracking — verify minimum wall for the flaring tool per the fitting manufacturer’s specification
- GTAW (TIG) welding: The preferred welding method for aluminium tube and fitting fabrication. Filler wire selection: ER4043 (Al-Si) for 6061 (easy welding, good crack resistance) or ER5356 (Al-Mg) for 5083 and for better anodise colour match. GTAW of 6061-T6 tube: the weld HAZ softens to approximately T4 or O temper strength — use the annealed UTS (125 MPa for 6061) to calculate the pressure rating of welded sections, not the T6 value (310 MPa). For pressure-rated aluminium circuits: prefer compression or flare fittings over welded joints to maintain the T6 temper pressure rating throughout the circuit
- Brazing: Aluminium brazing (600–620°C with Al-Si filler) is used for aluminium heat exchanger assembly and aluminium pneumatic manifold internal channel fabrication — the braze temperature is close to the aluminium melting point (660°C for 6061), so precise temperature control is critical to prevent base metal melting. Not a common EPC site joining method — typically a factory or shop process. Post-braze heat treatment can partially restore temper strength lost during the brazing thermal cycle
- Thread connections (NPT / BSP): Aluminium fittings with threaded connections use the same NPT (ASME B1.20.1) or BSP (ISO 7-1) thread forms as steel fittings. Aluminium thread strength is lower than steel — maximum torque values for aluminium NPT connections are significantly less than for steel; over-torquing causes thread stripping. Use calibrated torque wrench for all aluminium NPT/BSP connections; never use pipe wrenches or impact tools on aluminium threaded fittings
Industry Applications
& Documentation
RR Hydraulic maintains full traceability from certified billet to finished aluminium tube and fitting shipment. OD and wall gauging, temper hardness, pressure testing, alloy PMI, surface treatment verification, and complete export documentation are standard on all project-grade aluminium supply.
4.1 — Inspection & QC Protocol
4.2 — EN 10204 / Material Certification Requirements
| Certificate | Content | EPC Requirement | When Mandatory |
|---|---|---|---|
| 2.1 / 2.2 | Declaration / non-specific | Not acceptable for EPC pressure components | Never for hydraulic, process, or structural aluminium |
| 3.1 (EN 10204) | Heat-traceable mech + chem | Mandatory — all EPC aluminium | All process, hydraulic, and offshore aluminium components |
| 3.2 (EN 10204) | 3.1 + TPI countersign | Offshore critical; food-grade; aerospace | Marine/offshore; food-contact; safety-class |
4.3 — Applications by Industry
Mobile Hydraulic and Pneumatic Systems
6061-T6 aluminium tube (OD 6–25 mm, wall 1.5–3.0 mm) with aluminium DIN 24° or JIC 37° compression fittings for hydraulic and pneumatic circuits in mobile equipment — agricultural machinery, construction plant, materials handling, and mining equipment. The weight saving of aluminium vs steel tube is significant on mobile equipment where every kilogram of system weight reduces payload or increases fuel consumption over the equipment’s service life. 6061-T6 aluminium tube provides adequate working pressure for all standard mobile hydraulic circuits (up to 250–350 bar pilot line pressure). For the main high-pressure hydraulic circuit above 350 bar: use carbon or stainless steel tube — 6061-T6 aluminium at these pressures requires very heavy wall thicknesses that eliminate the weight advantage over steel.
Aluminium Pneumatic Cylinder Body Profiles
6063-T6 or 6061-T6 extruded aluminium profiles for ISO 15552 and VDMA 24562 pneumatic cylinder bodies — extruded with integral tube bore (the smooth bore used for piston seal travel), tie rod grooves, and port boss profiles, hard anodised to provide a wear-resistant bore surface. The hard anodised aluminium bore (45–65 µm Type III layer, 400–600 Vickers) eliminates the need for a steel liner in pneumatic cylinders operating at standard pressure (up to 10 bar working pressure). Hard anodised aluminium cylinder bores in well-maintained instrument air systems (ISO 8573-1 Class 1 air quality) achieve 10+ million cycle life without significant bore wear. For cylinders operating in contaminated air environments: specify steel-lined aluminium cylinders or full stainless cylinders.
Offshore and Marine Aluminium Piping (5083)
5083-H111 or H321 aluminium piping (ASTM B241 extruded seamless tube) for seawater cooling systems, ballast water treatment piping, and non-hydrocarbon process services on offshore FPSO and platform topsides where weight reduction is a design requirement. 5083 provides seawater corrosion resistance without the cathodic protection requirements of carbon steel seawater piping — the Mg content (4.0–4.9%) provides sufficient cathodic protection for the alloy to resist pitting in seawater at ambient temperatures. For seawater above 60°C: stress corrosion cracking of 5083 in H321 temper becomes a concern — specify sensitisation-resistant H111 temper or reduce temperature below 60°C. Join 5083 piping by GTAW welding with ER5356 filler (matching alloy); specify weld NDE per ASME B31.3 or DNV piping standard as applicable.
Food, Beverage, and Pharmaceutical Aluminium
1050 or 1100 pure aluminium tube (Type II anodised or electropolished) for food and beverage product transfer piping in breweries, dairy plants, confectionery production, and fruit processing facilities — where aluminium’s FDA compliance (GRAS for dry food contact; AP(2013)5 compliant for drinking water per national approvals), lightweight, easy fabrication, and natural corrosion resistance provide advantages over stainless steel. Aluminium is not suitable for all food applications — acidic products (citrus juice, vinegar, tomato) attack aluminium rapidly; highly alkaline cleaning chemicals (caustic soda CIP) dissolve aluminium. Confirm pH compatibility of all process fluids and CIP chemicals with the aluminium alloy before specifying. For pharmaceutical clean-room applications: electropolished 6061-T6 aluminium or PTFE-lined aluminium tube provides the required surface cleanliness without the cost of SS 316L.
Aerospace Hydraulic Fittings and Tube (2024 / 7075)
2024-T4 or 7075-T6 aluminium hydraulic tube and AN/MS fitting assemblies for aircraft hydraulic circuits (landing gear actuation, flight control surfaces, braking systems) — the weight saving of aluminium vs stainless steel hydraulic tubing on a commercial aircraft is measured in hundreds of kilograms, directly reducing fuel consumption and CO₂ per revenue tonne-kilometre. Aerospace aluminium fittings per SAE AS4395 (AN flared fittings, MS flareless fittings) are precision-machined from 6061-T6 or 2024-T4 alloy with surface protection (anodise + paint or Alodine) and qualified per AS9100 / NADCAP production control. Hydraulic fluid compatibility with aluminium in aerospace: Skydrol phosphate ester is NOT compatible with aluminium — specify titanium or steel fittings for Skydrol hydraulic systems; Mobil Aero HFA and AeroShell Fluid 41 mineral oil are compatible with aluminium.
Hydraulic Manifold Blocks and Valve Bodies
6061-T651 aluminium plate (stress-relieved by stretching — reduced residual stress for stable machining) CNC-machined into hydraulic manifold blocks, valve bodies, cylinder heads, and distribution plates for industrial hydraulic and pneumatic systems. Aluminium manifold blocks for mobile and industrial hydraulic systems: typically rated to 210–280 bar working pressure at 6061-T6 yield strength; hard anodised bore surfaces for wear resistance on valve spool and poppet seating faces. For high-pressure systems above 350 bar: ductile iron, steel, or stainless manifold blocks are required — 6061-T6 aluminium achieves adequate working pressure but the thicker wall required at high pressure eliminates most of the weight advantage over steel. Aluminium manifold blocks for pneumatic systems (up to 12 bar): anodised 6061-T6 is the standard — maximum weight saving, excellent machinability, and full pressure integrity for pneumatic service.
4.4 — Export Packaging Specification
- Aluminium tube supplied in straight lengths (typically 3 m or 6 m) bundled in polypropylene strap-bound bundles with both tube ends capped — open aluminium tube ends accumulate moisture, aluminium oxide particles, and contamination during transit that cannot be blown out without cleaning; end caps are mandatory for all pressure-service aluminium tube supply
- Hard-anodised and precision-machined aluminium fittings and manifold blocks individually wrapped in VCI-free polyethylene foam and packed in individual compartment trays — hard anodise surfaces are brittle and susceptible to chipping from metal-to-metal contact during shipping; individual cushioned packaging prevents chip damage to sealing surfaces and precision bores
- Aluminium tube and fittings must be segregated from copper, brass, and steel hardware in all packaging and storage — bi-metallic contact in humid conditions creates galvanic corrosion on the aluminium surface at the contact zone; even packaging tape or stainless steel wire ties touching bare aluminium in a humid container can initiate crevice corrosion over a 3–4 week ocean freight transit
- Food-grade aluminium components: clean-room packed in heat-sealed polyethylene bags immediately after surface treatment — any contamination of the food-contact surface after cleaning must be prevented; include FDA compliance declaration inside the sealed package so it is accessible at the destination without opening the hygienic packaging
- Heat number marked on each tube length and each fitting body — aluminium alloy and temper are not distinguishable by appearance; without heat number traceability, 6063-T6 and 6061-T6 tubes are identical in appearance but have 30% different yield strength. On bulk tube shipments: heat number stencilled on the outer tube of each bundle, and on the bundle strap-binding paperwork
- ISPM-15 timber or export cartons; VCI-inhibited packaging for ocean freight in humid tropical destinations; documentation in waterproof pocket: EN 10204 3.1/3.2 MTC, ASTM B210/B241 test report, mechanical test certificate, hardness report (temper verification), XRF/PMI report, dimensional certificate (OD and wall), pressure test certificate (hydraulic components), surface treatment report (anodise thickness, salt spray), RoHS/REACH declaration, FDA compliance (food-grade), FAI report
4.5 — Complete Documentation Package for Aluminium Supply
| # | Document | Standard / Format | Mandatory / Conditional | Notes |
|---|---|---|---|---|
| 01 | Material Test Certificate | EN 10204 3.1 / 3.2 or ASTM mill cert | Mandatory — all EPC aluminium | Alloy + temper; heat traceable; one MTC per heat |
| 02 | Chemical Composition Report | ASTM B210 / EN 573-3 alloy limits | Mandatory | All alloying elements; Cu content critical for 6061 vs 6063 |
| 03 | Mechanical Properties Report | ASTM E8 / EN ISO 6892-1 | Mandatory | UTS, yield (0.2% proof), elongation; per temper minimum |
| 04 | Temper Hardness Report | ISO 6506 Brinell / ASTM E10 | Mandatory — hydraulic and pressure components | 6061-T6: 90–100 HB target; lot basis |
| 05 | Dimensional Inspection Report | ASTM B210 / EN 754 tolerances | Mandatory — hydraulic precision tube | OD, wall thickness, ovality; lot basis |
| 06 | Hydrostatic Pressure Test Certificate | ISO 4413 proof at 1.5× WP; ISO 1167 | Mandatory — hydraulic fittings and manifolds | 100% for machined hydraulic components; sampled for tube |
| 07 | PMI Report (XRF) | XRF per lot — alloy verification | Mandatory — all EPC aluminium lots | 6061 vs 6063 vs 5083 vs 2024 vs 7075 differentiation |
| 08 | Surface Treatment Report | ISO 2360 (anodise thickness); ASTM B733 (ENP) | Mandatory — anodised / coated components | Thickness measurement; salt spray cert (offshore) |
| 09 | RoHS / REACH Declaration | EU 2011/65/EU; EU 1907/2006 | Mandatory — European EPC projects | Cr(VI) exclusion confirmation; SVHC list |
| 10 | FDA Compliance Declaration | 21 CFR 175.300 / GRAS confirmation | Conditional — food and pharma contact | Alloy-specific; not generic; post-anodise if applicable |
| 11 | Salt Spray Corrosion Certificate | ISO 9227 — per coating type (hours) | Conditional — marine / offshore / FPSO | Pass/fail at required hours per coating specification |
| 12 | First Article Inspection (FAI) Report | Project-specific format | Mandatory — new project specifications | All parameters; before batch production |
| 13 | TPI Witness Certificate | SGS / BV / DNV / Lloyds | Conditional — offshore; food-grade; aerospace | Co-witness pressure test + dimensional + PMI |
| 14 | ISO 9001:2015 Certificate | Third-party QMS certification | Mandatory — EPC projects | Scope covers aluminium tube and fitting manufacture |
| 15 | Country of Origin + Packing List | Chamber of Commerce / item-level | Mandatory | HS tariff code; alloy grade on packing list per item |
| 16 | Commercial Invoice + Bill of Lading | Per INCOTERMS 2020 | Mandatory | Freight forwarder issued |
4.6 — ISO and Quality System Compliance
ISO 9001:2015
Quality Management System covering aluminium billet procurement and heat traceability, drawing or extrusion process qualification (die geometry, reduction ratio, drawing speed), heat treatment process control (solution heat treatment temperature and time; quench rate; ageing temperature and time — all critical for achieving correct temper), dimensional inspection procedure (OD laser gauge, wall UT, ovality), hardness testing procedure (temper verification), XRF/PMI procedure, pressure test procedure, surface treatment process control (anodising bath composition, current density, temperature, time; sealing process; thickness measurement), and full material traceability from raw billet heat to dispatched tube or fitting. Mandatory for all EPC, offshore, food-grade, and aerospace aluminium supply.
ASTM B210 / EN 754 / EN 573
ASTM B210 and EN 754 define the tube geometry, dimensional tolerances, temper designations, and mechanical property minimums for drawn aluminium tube — the foundational procurement standards for aluminium hydraulic and pneumatic tube. EN 573 defines the European alloy chemical composition limits (EN-AW designation system). All three must be cited on the procurement specification for unambiguous aluminium tube procurement: ASTM B210 for OD/wall/temper; ASTM E8 for mechanical testing method; ASTM B210 for composition limits (or EN 573 for European projects). A specification that only cites “6061-T6 aluminium tube” without the dimensional standard is incomplete — the manufacturer cannot determine the applicable OD tolerances, wall tolerances, or test requirements without the full standard citation.
ISO 4413 / ISO 4414
ISO 4413 (Hydraulic fluid power) and ISO 4414 (Pneumatic fluid power) — the safety standards governing aluminium tube and fitting use in hydraulic and pneumatic systems. Both standards specify the minimum safety factor requirements (4:1 burst-to-working-pressure for hydraulic; 4:1 for pneumatic), the materials acceptable for the system working pressure and temperature, and the pressure testing requirements for new installations. ISO 4413 Section 5.4 explicitly identifies aluminium alloys as acceptable materials for hydraulic tube and fittings within the working pressure calculated from the tube dimensions and alloy strength — and explicitly excludes aluminium from service with alkaline (pH > 9) hydraulic fluids such as water-glycol HF-C type and phosphate ester HF-D type fire-resistant fluids.
MIL-A-8625 / AMS Specs (Aerospace)
MIL-A-8625 (Anodic Coatings for Aluminium and Aluminium Alloys) defines the Type I (chromic acid), Type II (sulphuric acid), and Type III (hard anodise) anodising processes and the performance requirements for each type. For aerospace and defence aluminium fittings and manifolds: MIL-A-8625 is the governing surface treatment standard — aerospace quality programmes (AS9100 / NADCAP) require chemical processing per MIL-A-8625 with NADCAP-accredited anodising suppliers. AMS (Aerospace Material Specifications) 2770 governs the heat treatment process for aerospace aluminium alloys (solution temperature, quench rate, ageing temperature and time) and AMS 2750 governs the pyrometry requirements for heat treatment furnaces — together these AMS specifications ensure the T6 temper is correctly achieved and verified for safety-critical aerospace aluminium components.
Submit your OD, wall, alloy, temper, surface treatment, and quantity to RR Hydraulic for a complete, certified commercial offer.