In one paragraph: 6061-T6 is the all-round aluminum — ~310 MPa tensile strength, excellent corrosion behavior, weldable, and the best alloy for dyed anodizing. 7075-T6 is the strength alloy — ~570 MPa tensile, favored in aerospace and robotics — but it welds poorly, corrodes more readily, and anodizes darker and less predictably. Choose 7075 only when the strength saves weight or size; otherwise 6061 is the cheaper, friendlier default.
The numbers that matter
| 6061-T6 | 7075-T6 | |
|---|---|---|
| Tensile strength | ~310 MPa | ~570 MPa |
| Yield strength | ~276 MPa | ~500 MPa |
| Density | 2.70 g/cm³ | 2.81 g/cm³ |
| Corrosion resistance | Very good | Fair (needs coating) |
| Weldability | Good | Poor (typically bolted/bonded) |
| Anodizing appearance | Even, takes color well | Darker, less predictable |
When 7075 earns its price
- Weight-critical structural parts — arms, brackets and mounts where a smaller section at higher stress saves real mass (robotics, drones, aerospace).
- Fatigue-loaded fittings — the strength margin pays off in cyclic loading.
- High-load gears and cams — where 6061 would deform.
When 6061 is simply correct
- Enclosures and cold plates — thermal conductivity is comparable, corrosion behavior better, and it brazes/welds into assemblies (cold-plate material logic).
- Parts that get anodized in brand colors — even, repeatable appearance.
- Any welded structure — 7075’s hot cracking makes welded 7075 a reliability risk.
The machining angle
Both alloys machine cleanly; 7075 gives slightly better chip control and allows thinner walls at the same rigidity — useful for deep pockets. The bigger difference is downstream: 7075’s copper content means bare surfaces corrode in humid environments, so plan a finish (anodize, chromate) into the BOM rather than treating it as optional. Coating specifics: Type II vs Type III anodizing.
Rule of thumb
If you cannot name the reason you need 7075, use 6061. Specify the temper on the drawing (T6 is not the only option — T651 saves machinists stress-relief grief on plate stock). Material selection is part of every DFM review here — send the drawing with your working grade and we will confirm or challenge it before quoting.
