The alloys, and when each earns its place
| Alloy | Character | Choose it for |
|---|---|---|
| 6082 / 6061 | The general-purpose workhorses: good strength, machinability, weldability and corrosion resistance; 6082 is the common UK stock | Brackets, housings, plates, fixtures, most machined aluminium parts |
| 7075 | Aerospace-grade strength approaching mild steel, at aluminium weight; dearer, less weldable, less corrosion tolerant | Highly loaded parts where weight matters: motorsport, actuation, tooling |
| 5083 | Excellent seawater corrosion resistance, good as heavy plate, weldable | Marine and subsea housings, welded fabrications, large flat parts |
| 2011 | Free-machining: chips beautifully on lathes; poor weldability and corrosion resistance | High-volume turned parts, fittings and inserts |
| Cast plate (e.g. 5083-based tooling plate) | Stress-relieved and stable: machines flat and stays flat | Baseplates, fixtures, gauges and anything that must not move after machining |
As with stainless, specify "6082-T6 or equivalent" and let the shop use certified stock they hold. The T-condition matters: T6 is the solution-treated and aged state most structural parts want, and it belongs on the drawing, not in an email afterwards.
Why aluminium parts price well
Aluminium cuts fast: several times steel's cutting speed in the common alloys, with lower tool wear and easy chip evacuation. Cycle time is one of the five inputs in every machining price, so aluminium parts are routinely cheaper than the same geometry in steel even when the billet costs more per kilogram.
Two design habits push the price down further. Thin walls and deep pockets machine happily in aluminium, so weight-saving geometry that would be a nightmare in steel is routine, but chatter-prone features still deserve a DFM review before they are locked in. And stock sizes matter as everywhere: a part designed one millimetre over a standard plate thickness buys the next size up and machines the difference into swarf.
Tolerances behave conventionally: the standard and precision bands in our tolerance guide apply, with one aluminium-specific note. The material moves with temperature noticeably more than steel, so very tight fits on large aluminium parts want measuring, and agreeing, at a stated temperature.
The anodising catch, explained before it costs you
Anodising grows a controlled oxide layer on the surface: decorative anodising for corrosion resistance and colour, hard anodising for genuine wear resistance at greater thickness. Three things surprise first-time buyers.
The alloy shows. 6082 and 6061 anodise beautifully and consistently. 2011 and some 7075 tempers anodise darker, patchier or duller, and castings can mottle. If cosmetic anodising matters, say so before the alloy is chosen, not after.
The surface shows. Anodising reproduces the underlying texture faithfully: machining marks that were acceptable bare become visible under a clear coat. Cosmetic faces need their surface finish achieved before the tank.
The dimensions move. Hard anodising adds real thickness, roughly half of it outward growth, so toleranced bores and fits must be machined to allow for the coating. This is a routine calculation when machining and finishing are coordinated as one order, and a goods-inward argument when they are not.
How TrueNorth supplies aluminium
Machining and anodising as one order is the point. TrueNorth coordinates machining, anodising or painting, and inspection through vetted UK shops, with the coating allowances, alloy and finish choices resolved at the DFM review rather than discovered at delivery. One quote, one price for the delivered, inspected part, with material certificates in the traceability pack where specified.
The aluminium work that suits us runs from electrification and data centre hardware, enclosures, heatsink blanks, busbar supports, through machine builders' fixtures and housings to automotive aftermarket parts. Send the drawing with quantities and the finish you want, and the quote lands within 48 hours.