Metal tanks are among the highest-consequence components on a heavy truck. An air reservoir failure can cause total loss of braking pressure. A fuel tank failure can ground a vehicle or — in worst cases — create a fire hazard. Yet procurement decisions for metal tanks are often driven by price and dimensional fit alone, with material specification and manufacturing quality treated as assumptions rather than verifiable facts.
This guide covers the main categories of heavy truck metal tanks, the material and quality standards that govern them, and what to verify before placing a bulk order.
Metal Tank Types in Heavy Trucks
Heavy truck metal tanks fall into three main categories, each with distinct structural and regulatory requirements.
Air Reservoirs
Air reservoirs store compressed air for brake and suspension systems. On a typical Euro 5/6 tractor-trailer configuration, there are multiple reservoirs — primary and secondary brake circuits, parking brake, and suspension — each sized to maintain system pressure during repeated actuation without compressor recovery.
Key parameters: capacity (litres), working pressure (typically 1.25 MPa / 12.5 bar for Chinese-market OEM), material (aluminium alloy 5083-H111 or welded steel), and mounting configuration.
Governing standard in China: QC/T 200-2015 (Performance Requirements and Test Methods for Air Reservoirs Used in Air Brake Systems).
Fuel Tanks
Fuel tanks on heavy trucks range from standard rectangular aluminium tanks to shaped and baffled designs for specific chassis configurations. ADR (hazardous goods) vehicles require explosion-proof tanks with additional venting and grounding specifications.
Key parameters: capacity (litres), material (aluminium alloy or steel), wall thickness, baffle configuration, sender unit port specification, and — for ADR applications — explosion-proof certification.
Welded Assemblies and Custom Fabrications
Beyond standard catalogue items, many fleet operators and OEMs require custom-fabricated tanks or bracket-integrated assemblies. These are specified by drawing rather than OE number, and sourced through a different procurement process — sample confirmation followed by bulk production.
Material Standards: Aluminium vs Steel
Most modern heavy truck tanks are aluminium. The shift from steel to aluminium over the past two decades was driven by weight reduction, corrosion resistance, and weldability — not cost. Aluminium tanks are more expensive to produce but outlast steel in corrosive environments and do not require internal coating against rust.
| Property | Aluminium (5083-H111) | Carbon Steel |
|---|---|---|
| Density | 2.66 g/cm³ | 7.85 g/cm³ |
| Corrosion resistance | Excellent (native oxide layer) | Poor without coating |
| Weld strength retention | High (ER5356 / ER4043 filler) | High |
| Weight saving vs steel | ~65% | Baseline |
| Typical use | Air reservoirs, fuel tanks, ADR tanks | Heavy-duty fuel tanks, frame-mounted tanks |
Steel tanks remain in use for applications where impact resistance or cost is prioritised over weight, or where the tank is protected from the environment by mounting position.
Why alloy grade matters: Not all aluminium is equal. Air reservoir OEM production in China uses 5083-H111 per GB/T 3880.1 — a marine-grade alloy chosen for weld strength retention and corrosion resistance. Suppliers substituting a lower-grade alloy (e.g. 3003 or 6061) for cost reduction will produce tanks that meet dimensional spec but fail pressure testing or corrode prematurely. Always request the mill certificate for the specific alloy grade.
Quality Verification: What to Check Before Ordering
Wall Thickness
Wall thickness is not a preference — it is determined by working pressure, tank diameter, and alloy properties via the hoop stress equation. For air reservoirs at 1.25 MPa working pressure, OEM production benchmarks are:
| Outer Diameter | Minimum Wall Thickness |
|---|---|
| 80–150 mm | 2.0 mm |
| 150–220 mm | 2.5 mm |
| 220–300 mm | 3.0 mm |
A supplier offering 1.5 mm wall on a 200 mm diameter reservoir is below the structural minimum for 12.5 bar service — regardless of any claimed certifications.
Weld Quality
Request weld procedure documentation and ask for the most recent ultrasonic or radiographic inspection report. Key indicators:
- Weld process: MIG (GMAW) with ER5356 or ER4043 filler is standard for aluminium OEM production
- Visual inspection: uniform bead profile, no porosity visible at the surface, full penetration at end caps
- NDT reports: OEM-level suppliers maintain records per QC/T 200-2015 requirements
Pressure Testing
QC/T 200-2015 requires:
- Hydrostatic test at 1.5× working pressure (1.875 MPa for 1.25 MPa-rated tanks), minimum 1 minute, no leaks
- Burst test minimum at 3× working pressure
- Fatigue test: 1,000,000 pressure cycles between 0.1 MPa and working pressure
Request test records with serial numbers traceable to the production batch.
Coating
Select coating based on operating environment:
| Coating | Salt Resistance | Temperature Range | Best For |
|---|---|---|---|
| Epoxy primer + polyurethane | Moderate | −40°C to +120°C | Dry climates, inland routes |
| Anodising + sealant | Good | −60°C to +150°C | Coastal, high-humidity |
| Two-component epoxy | High | −40°C to +100°C | Road salt, port operations |
For European markets where road salt is used in winter, anodising or two-component epoxy is the appropriate specification.
Supplier Evaluation Checklist
Before placing a bulk order, request the following from any supplier:
- Engineering drawings with wall thickness called out per diameter
- Mill certificate for the alloy batch (5083-H111 or equivalent)
- Hydrostatic test records for the last three production batches
- Weld procedure specification and welder qualification records
- QC/T 200-2015 compliance certificate or equivalent
- Coating specification: type, dry film thickness, salt spray test hours
Suppliers unable to provide any of the above do not meet minimum OEM-level quality requirements. A low unit price that comes with missing documentation is a liability, not a saving.
Guanda manufactures aluminium air reservoirs and fuel tanks to QC/T 200-2015 and supplies full technical documentation on request. Custom fabrication is available from drawing or sample. View metal tank products →
Further Reading
- Aluminum Air Reservoir Procurement Guide: How to Identify OE-Grade Quality Through Wall Thickness, Welding, and Coating — detailed specifications, OEM wall thickness benchmarks, and a complete procurement checklist for air reservoirs