Aluminum Rectangular Tubing Knowledge – 6061, 6063?

I know it can feel hard when you read about 6061 and 6063 tubing. You might feel lost choosing the right alloy.

6061 and 6063 are both common aluminum alloys. 6061 has higher strength, while 6063 is easier to form and has a smoother profile finish.

Stay with me and I will explain how they differ and which one works best in different uses.

What is the difference between 6061 and 6063 tubing?

I often see customers confuse these alloys. They think they are almost same. I will break the key differences in simple parts.

6061 tubing is stronger and better for structural use, while 6063 tubing is easier to extrude, has better surface finish, and is often used in architectural and decorative applications.

I explain their composition, properties, and common uses below.

Composition and Temper

• 6061 contains magnesium and silicon, with small copper content.
• 6063 has magnesium and silicon only, lower strength alloy.
• Both can be heat-treated. Common tempers: T6 (full strength) and T5 (moderate).

Property Comparison

Common Applications

I often tell customers that if they need strength, they choose 6061. If they want clean visual finish and cost-effective extrusion, they go with 6063.

Which alloy is best for structural rectangular tubing?

I know many buyers check strength, stiffness, and weldability. Let me explain which works best in structural use.

6061, especially in T6 temper, is generally better for structural rectangular tubing because it offers higher tensile and yield strength, better stiffness, and deeper weld joints.

I break reasons below and how they matter in building frames and load systems.

Structural Strength

6061-T6 delivers higher load capacity. You can calculate section modulus. It resists bending and deflection better than 6063-T6. It performs well in building and industrial frame use.

Welded Joints and Temper Impact

6061 tends to lose some strength near welds due to heat-affected zone. But post-weld heat treatment or solution stress relief can help.
6063 softens more in weld area. It recovers quickly but offers lower base strength.

Stiffness and Safety Factor

In beams or frames, stiffness matters. Even though both alloys have similar modulus of elasticity (~10 Mpsi), the higher yield point of 6061 gives better load margin for safety.

Summary Table

I once supplied 6061 square tubing for a steel replacement frame. It supported high loads with less deflection. The customer got lighter and stiffer structure. We would not pick 6063 for that job.

How do 6061 and 6063 compare in strength and corrosion?

I know customers ask how they hold up over time, especially outdoors or in moist conditions. I explain both properties below.

6061 is stronger and handles load better. Both alloys resist corrosion, but 6063 often has slightly better natural corrosion resistance due to higher silicon content and smoother surface after anodizing.

I explain corrosion and strength aspects side by side.

Strength Differences

6061 has higher tensile strength (~45 ksi) and yield (~40 ksi).
6063 is softer (~35 ksi tensile, ~30 ksi yield).
That means 6061 can take more load before permanent deformation.

Corrosion Resistance

Both alloys form a natural oxide layer which prevents corrosion. After anodizing, corrosion protection improves.
6063 tends to have finer grain structure and smoother finish. This helps seal surface and reduce corrosion risk.
6061 still resists corrosion well, but joint edges or rougher finishes may create weak spots.

Practical Example

If tubing sits outdoors in humid coastal area, both withstand salt air. A 6063 anodized profile may maintain its look longer. A 6061 profile with low-quality finish might show more staining over time.

Comparison Table

By choosing clean extrusion and proper anodizing, both alloys last long. But 6063 may be easier to keep rust-free visually.

Is 6061 or 6063 easier to machine and weld?

I often get asked about fabricating with these alloys. People want to know which one cuts, mills, or welds easier.

6063 is easier to extrude and often machines smoother, but 6061 offers better weld strength and handles more tool abuse. Both weld well, but each has pros depending on application.

I explain machining and welding behavior below in detail.

Machining Tips

6061 machines very well with CNC mills, lathes, and drills. It holds tight tolerances.
6063 also machines well, especially for finishing cuts and light milling. Its softer nature means lower tool wear.
For fine surface finish or light feed rates, 6063 can yield smoother edges.
However, 6061 resists chatter and is better under heavier cutting loads.

Welding Behavior

• TIG welding: Both are weldable with TIG.
  • 6061 needs filler like 4043 or 5356. Be careful of porosity.
  • 6063 heats and cools fast, weld puddle is fluid. It requires skill to avoid burn-through on thin wall tubing.
• MIG welding: 6061 responds well to spool-gun MIG, can produce strong joints.
  6063 welds easily but strength at joint is lower.
• Post-weld, neither regains full T6 hardness unless you heat treat again.
  6063 softens but recovers quickly. 6061 retains better strength after weld zone if treated.

Summary Table

I remember a client who wanted quick prototypes. We used 6063 because we could mill and shape quickly. For another client building structural supports, we used 6061. It held up better after welding and passed all load tests.

Conclusion

I compare 6061 and 6063 tubing by strength, corrosion, weldability, and machining. 6061 is stronger and better for structural use. 6063 is easier to extrude, gives smoother finish, and is often better for architectural or decorative work. Both weld and machine well, but choice depends on your needs.