Stretch bending
Trim follows body curves by stretch-forming over a die. 5657 in H112 or O elongates evenly without orange peel, which would show after polishing.
Automotive bright trim
5657 Aluminium Extrusions and Trim for Automotive
5657 is a high-purity aluminium-magnesium alloy made for one job: bright, mirror-like trim that keeps a clear, colourless anodic finish. Car makers use it for window surrounds, grille bars, roof-rail covers and badge mouldings. Metline supplies 5657 extruded trim sections, strip and sheet to drawing, ready for chemical brightening and anodising, to trim makers worldwide.
- Alloy
- 5657 (Al-0.8Mg, high purity)
- Tempers
- H112, O, H25, H28
- Forms
- Trim extrusions, strip, sheet
- Finish
- Bright dip + clear anodise
What makes 5657 a trim alloy?
Ordinary aluminium alloys turn hazy or slightly grey when anodised, because iron, silicon and manganese form intermetallic particles that scatter light inside the oxide film. 5657 is built on a high-purity base (roughly 99.5 % aluminium before the magnesium addition) and limits iron to 0.10 % and silicon to 0.08 %. With so few particles, a chemically or electrolytically brightened surface stays brilliant after anodising.
The 0.6 – 1.0 % magnesium addition does two things. It raises strength above that of pure aluminium so that thin trim keeps its shape, and it stays in solid solution rather than forming particles, so it does not cloud the finish. The result is a soft, very formable alloy that polishes like a mirror and anodises to a clear, water-white coating.
Automotive trim is usually extruded or roll-formed in the as-fabricated or lightly work-hardened condition, bent and stretch-formed to the body contour, then polished, bright-dipped and anodised. 5657 tolerates this whole sequence better than general-purpose alloys such as 6063, which is cheaper but gives a slightly warmer, less reflective finish.
5657 chemical composition (wt %)
Limits are the registered Aluminum Association values, also adopted in EN 573-3 as EN AW-5657 (AlMg0,8). Note the tight caps on iron, silicon, copper and manganese: they are what separates a bright-trim alloy from a general-purpose one. The mill certificate reports the analysis of each lot.
| Element | Limit | Why it matters for trim |
|---|---|---|
| Magnesium (Mg) | 0.6 – 1.0 | Solid-solution strengthening without clouding the oxide |
| Silicon (Si) | 0.08 max | Kept very low to avoid grey Si particles in the film |
| Iron (Fe) | 0.10 max | Fe-rich particles are the main cause of haze |
| Copper (Cu) | 0.10 max | Higher Cu yellows the anodic film |
| Manganese (Mn) | 0.03 max | Mn gives a brownish tint after anodising |
| Zinc (Zn) | 0.05 max | |
| Gallium (Ga) | 0.03 max | Trace control for brightening response |
| Vanadium (V) | 0.05 max | |
| Others, each / total | 0.02 / 0.05 | Tighter than most alloys |
| Aluminium (Al) | Remainder | About 98.5 – 99.4 % |
Mechanical and physical properties
5657 is not heat-treatable; it gains strength only by cold work. H25 (strain-hardened and partly annealed) is the usual starting temper for formed sheet trim, while extruded sections are normally supplied in H112 and gain a little strength as they are stretch-formed. Values below are typical, not guaranteed minimums.
| Temper | Tensile strength | Yield strength (0.2 %) | Elongation | Typical use |
|---|---|---|---|---|
| O (annealed) | about 110 – 130 MPa | about 40 – 60 MPa | 20 % or more | Deep-formed or spun trim |
| H112 (as extruded) | close to O-temper values | agreed on order | high | Extruded mouldings and window surrounds |
| H25 | 160 MPa | 140 MPa | about 11 – 12 % | Roll-formed and stamped sheet trim |
| H28 | about 190 MPa | about 165 MPa | about 7 % | Flat or lightly formed reflectors and trim |
Typical values from the Aluminum Association and published handbook data; order-specific limits are agreed with the trim maker and shown on the certificate.
Physical properties
- Density
- 2.69 – 2.70 g/cm³
- Thermal conductivity
- about 205 – 210 W/m·K
- Electrical conductivity
- about 54 % IACS
- Modulus of elasticity
- about 69 GPa
- Melting range
- about 635 – 655 °C
5657 trim sections, strip and sheet we supply
Supply range
- Extruded trim
- Custom open and semi-hollow sections to drawing; wall typically about 1 – 3 mm
- Simple shapes
- Flat bar, angles, channels, small round and rectangular tube for trim and fittings
- Strip and sheet
- Roughly 0.3 – 3 mm thick, slit coil or cut sheet in O, H25 or H28
- Length
- Extrusions usually cut to about 3 – 6 m, or to the stretch-forming blank length
- Surface
- Mill finish protected by film, ready for polishing, bright dip and anodising
- Standards
- ASTM B221 / EN 755 for extrusions, ASTM B209 / EN 485 for sheet, or the OEM material specification
Bright-trim sections need an extrusion die and surface quality agreed in advance. Send the drawing and finish specification with your enquiry.
Surface quality is the main purchasing criterion for 5657. Specify the visible faces, the acceptable level of die lines and handling marks, and whether profiles must be interleaved or individually wrapped. A defect that is invisible on mill finish can show clearly after bright dipping, so inspection is best agreed on a brightened and anodised sample.
Forming, brightening and anodising 5657 trim
Mechanical polishing
Buffing removes die lines and handling marks before brightening. Keep polishing pressure moderate to avoid heat discolouration.
Chemical brightening
Phosphoric-nitric bright dips or electropolishing level the surface to a mirror; the high-purity base makes this step far more effective than on 6063.
Clear anodising
Sulphuric-acid anodising to a thin, sealed film gives a transparent, colourless layer. Exterior trim commonly uses about 5 – 10 µm, balancing brightness and durability.
Corrosion testing
OEM specifications often call for CASS or salt-spray testing and alkaline car-wash resistance on finished parts; plan these with the anodiser.
Joining
Trim is usually clipped or bonded rather than welded. If welding is unavoidable, use matching high-purity filler, as standard fillers anodise to a different shade.
SAE J399 notes that a fully annealed, recrystallised grain structure is not ideal for bright anodising, which is one reason sheet trim is often formed from an intermediate temper such as H25 rather than O.
Where 5657 is used on vehicles
- Window and door surrounds: beltline mouldings and window-frame finishers
- Grille trim: bright grille bars, surrounds and accent strips
- Roof rails and roof-rail covers: where a bright anodised finish is wanted
- Body-side and bumper mouldings: accent strips bonded to painted panels
- Interior trim: door-sill plates, dashboard inlays and console accents
- Lighting: reflector bezels and lamp trim rings that need high reflectance
- Badges and nameplates: stamped and anodised emblems
A typical premium window surround is extruded in 5657, stretch-formed, polished, bright-dipped and anodised to a clear film, then fitted with clips. The same alloy in H25 sheet is roll-formed for thinner accent strips so that both parts match in colour.
5657 compared with 5457, 5252 and 6063 for trim
| Property | 5657 | 5457 | 5252 | 6063 (bright grade) |
|---|---|---|---|---|
| Magnesium (typical) | 0.6 – 1.0 % | 0.8 – 1.2 % | 2.2 – 2.8 % | 0.45 – 0.9 % (with Si) |
| Iron limit | 0.10 % | 0.10 % | 0.10 % | 0.35 % |
| Anodised brightness | Highest | Very high | Very high | Good |
| Strength | Low | Low–medium | Medium | Medium (heat-treatable) |
| Formability | Excellent | Excellent | Very good | Good |
| Typical form | Sheet, trim extrusion | Sheet, trim | Sheet | Extrusion |
Choose 5657 when brightness and colour match matter most. 5457 and 5252 give more strength for trim that must resist denting, at a small cost in brilliance. 6063 is cheaper and easier to extrude in complex shapes, but its higher iron limit gives a less reflective finish; it suits satin or coloured anodised trim better than mirror trim.
How to order 5657 trim from Metline
- SpecifyAlloy and temper (5657-H112 for extrusions, H25 or H28 for sheet), drawing or strip size, length, visible faces and finish requirement, and annual volume.
- Confirm the standardASTM B221 or EN 755 for extrusions, ASTM B209 or EN 485 for sheet, or the OEM's own trim material specification.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your plant or port.
- Process and inspectProfiles are cut, interleaved or wrapped to protect visible faces, and checked for dimensions and surface quality; brightened and anodised trial pieces can be arranged for approval.
- Document and shipEach lot ships with an EN 10204 3.1 mill test certificate, lot traceability and a packing list, in seaworthy export packing. Third-party inspection can be arranged on request.
References and standards
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- SAE J399 – Anodized Aluminum Automotive Parts
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- ASTM B209 – Aluminum and Aluminum-Alloy Sheet and Plate
5657 automotive trim aluminium: frequently asked questions
Why is 5657 used for bright automotive trim?
Its iron, silicon, copper and manganese are held to very low levels, so almost no intermetallic particles form. After chemical brightening and anodising, the coating stays clear and mirror-like instead of turning hazy.
Can 5657 be heat-treated for more strength?
No. 5657 is a non-heat-treatable Al-Mg alloy. Strength comes from cold work, so the temper (O, H25, H28) or the stretch-forming strain sets the final strength.
What is the difference between 5657 and 5457?
Both are high-purity bright-trim alloys. 5457 carries a little more magnesium and a small manganese allowance, so it is slightly stronger; 5657 gives the clearest, brightest finish.
Is 5657 aluminum available as extrusions?
Yes. 5657 is mostly rolled into sheet, but trim sections are extruded in H112 to drawing for window surrounds, grille bars and mouldings. Die and surface quality are agreed before production.
How thick should the anodic film be on exterior trim?
Exterior bright trim commonly uses a thin, sealed sulphuric-acid film of roughly 5 – 10 µm. Thicker films resist wear better but lose some brightness; the OEM specification sets the final value.
Do you supply 5657 outside India?
Yes. Metline ships 5657 trim sections, strip and sheet worldwide with mill certificates and export packing that protects the visible faces.
Need 5657 bright trim sections?
Send the drawing, temper, finish requirement and volume. Our team will reply with feasibility, certification and a delivered price.
