Aluminum 1090: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

1090 aluminum is in the 1xxx series of wrought aluminum alloys, representing the commercially-pure end of the spectrum with nominal aluminum content of 99.90% by mass. The 1xxx series is characterized by minimal alloying additions and is primarily alloyed only with trace elements that remain within tight impurity limits to preserve electrical, thermal, and corrosion performance.

Major alloying elements in 1090 are essentially impurities: silicon, iron, copper, manganese, magnesium, zinc, chromium, and titanium appear only in trace amounts and collectively influence mechanical characteristics. Strength in 1090 derives almost entirely from work hardening (strain processing) rather than heat treatment, because the alloy is non-heat-treatable; cold rolling and controlled annealing are the primary property-control tools.

Key traits of 1090 are high electrical and thermal conductivity, excellent corrosion resistance in many atmospheric and mildly corrosive environments, and superior formability in annealed tempers. Its weldability is very good for common fusion and resistance methods, and its mechanical strength is low compared with alloyed series but sufficient for sheet and foil applications where purity and conductivity dominate.

Industries that commonly specify 1090 include electrical transmission and busbars, chemical-processing equipment, reflective surfaces and lighting, foil and capacitor materials, and architectural or decorative panels. Engineers select 1090 when maximum conductivity, clean surface finish, or high formability are primary requirements and when the designer accepts lower structural strength in exchange for those properties.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (30–45%)	Excellent	Excellent	Fully annealed condition for maximum ductility
H12	Low–Medium	Moderate (15–30%)	Very Good	Very Good	Lightly strain hardened, moderate temper for formed parts
H14	Medium	Moderate–Low (8–20%)	Good	Very Good	Half-hard temper common for sheet that needs stiffness
H16	Medium–High	Low (5–12%)	Fair	Very Good	More strain hardening for higher strength and springback
H18	High	Low (2–8%)	Limited	Very Good	Full-hard, used where formability is not critical
H24	Medium	Moderate (10–25%)	Good	Very Good	Strain-hardened plus partial anneal for balance of ductility and strength

Temper has a direct and predictable effect on 1090 performance because properties are derived from cold work rather than precipitation strengthening. Moving from O to H18 increases yield and tensile strength at the expense of elongation and formability, so selection typically balances springback, forming complexity, and final strength targets.

Because the alloy does not respond to solution-and-age cycles, temper selection focuses on the degree of cold work and any intermediate annealing. Designers control forming and final geometry by specifying an appropriate H-temper or an annealed O condition for complex bends and deep draws.

Chemical Composition

Element	% Range	Notes
Si	≤ 0.10 (typical)	Silicon kept low to maintain ductility and conductivity
Fe	≤ 0.40 (typical)	Iron is the principal impurity; increases strength modestly but reduces conductivity and ductility
Mn	≤ 0.05	Very low to minimize second-phase formation
Mg	≤ 0.03	Kept minimal to prevent unintended strengthening and loss of conductivity
Cu	≤ 0.05	Copper minimized to preserve corrosion resistance and conductivity
Zn	≤ 0.03	Zinc limited to avoid intermetallics and stress corrosion tendencies
Cr	≤ 0.05	Trace concentrations used to control grain structure in some processing routes
Ti	≤ 0.03	Small additions may be used for grain refinement during casting/extrusion
Others (each)	≤ 0.05; total others ≤ 0.15	Collective trace impurities controlled to maintain commercial-purity classification

The chemical fingerprint of 1090 is defined by keeping alloying elements at trace levels so that the metal behaves much like pure aluminum. Trace iron and silicon have the largest influence: iron forms intermetallics that elevate strength slightly but can reduce ductility and conductivity, while silicon affects castability and solidification behavior if present. Controlling trace elements is essential to preserve the alloy’s electrical and thermal transport properties while delivering acceptable mechanical integrity.

Mechanical Properties

In tensile loading, 1090 displays relatively low ultimate tensile strength and yield strength in the fully annealed state, with high total elongation that enables deep forming and drawing operations. As the material is cold worked into H-tempers, tensile and yield strengths increase substantially, but ductility and elongation fall accordingly, producing higher springback and reduced bendability.

Hardness correlates with cold work; annealed 1090 shows low hardness values characteristic of pure aluminum, while H18 or similar tempers register appreciably higher hardness suitable for applications needing wear resistance or rigidity. Fatigue strength for 1090 is modest and depends strongly on surface finish and temper; polished, high-conductivity sections will perform better than rough, strained surfaces but remain below that of alloyed aluminum series used for structural fatigue-critical parts.

Thickness influences mechanical response: very thin foils (microns to tenths of a millimeter) will show higher apparent strength due to work hardening during rolling and manufacturing effects, while heavy gauge plate will be closer to bulk, annealed properties unless explicitly cold worked. Surface defects and residual stresses from forming strongly affect tensile and fatigue performance in this alloy.

Property	O/Annealed	Key Temper (e.g., H14/H18)	Notes
Tensile Strength	~60–110 MPa (typical range)	~100–160 MPa (depending on work hardening)	Values depend on thickness and exact cold-work level
Yield Strength	~20–60 MPa	~70–130 MPa	Yield increases significantly with H-tempers
Elongation	~30–45%	~2–20%	High in O, reduced by strain hardening
Hardness	~20–35 HV	~30–60 HV	Hardness rises with degree of cold work

Physical Properties

Property	Value	Notes
Density	2.71 g/cm³	Typical for aluminum; useful for mass and stiffness calculations
Melting Range	~660 °C (melting point)	Pure-aluminum melting point; alloying traces change solidification behavior slightly
Thermal Conductivity	~220–235 W/m·K	Very high; among the best for commercial aluminum alloys
Electrical Conductivity	~55–65% IACS	High conductivity makes 1090 suitable for busbars and conductors
Specific Heat	~0.90 J/g·K (900 J/kg·K)	Good heat-storage capacity for thermal design
Thermal Expansion	~23–24 µm/m·K	Typical linear expansion for aluminum at room temperature

1090’s physical properties make it attractive where heat dissipation or electrical conduction is a primary design driver. Thermal and electrical conductivities are suppressed only slightly by the trace impurities allowed in the specification, so 1090 behaves similarly to pure aluminum in most thermal-management applications.

The combination of low density and good thermal properties yields excellent specific thermal conductivity and specific stiffness for light-weight thermal designs. Designers should account for aluminum’s relatively high thermal expansion when joining dissimilar materials or when tight dimensional control over temperature cycles is required.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.2–6.0 mm	Sensitive to cold work; rolled gauge influences strength	O, H14, H16	Widely used for cladding, reflectors, and decorative finishes
Plate	>6.0 mm	Generally supplied annealed or lightly cold worked	O, H12	Thick plates used where conductivity and corrosion resistance are needed
Extrusion	Profiles up to several meters	Limited by low alloy content; work hardening during extrusion	O, H12	Common for simple sections; grain control via thermal treatment
Tube	Welded and seamless, various diameters	Mechanical properties influenced by forming and welding	O, H14	Tubing for lightweight frames, capacitors, HVAC components
Bar/Rod	Dia. 2–50 mm	Cold-drawn for higher strength	O, H14, H18	Used for conductive leads, fasteners, and machined parts

Processing differences across forms are driven by the alloy’s response to cold work and annealing. Sheet and foil rolling produce high ductility in the annealed condition and elevated strength through controlled cold reduction, while extrusions and extruded profiles may require special thermal cycles to control grain growth and surface quality.

Applications for each product form follow manufacturing economics and mechanical needs: thin gauge foil and sheet exploit high conductivity and formability, while thicker plate or extrusions use the alloy’s corrosion resistance where structural loads are moderate. Welding, brazing, and forming strategies vary by form and temper to avoid cracking or undue property loss.

Equivalent Grades

Standard	Grade	Region	Notes
AA	1090	USA	ASTM/AA designation for commercially-pure Al with 99.90% nominal Al
EN AW	1090	Europe	European designation often maps to the same chemical limits; check EN standard variants
JIS	A1090	Japan	Japanese grade with similar purity targets; minor tolerances may differ
GB/T	Al99.9	China	Chinese equivalents reference nominal 99.9% Al purity grades in standards

Subtle differences between regional specifications arise in permissible impurity limits, surface condition requirements, and mechanical property sampling methods. Engineers should verify the governing standard for contracts because allowable concentrations of iron and silicon, and the control of minor elements, can vary and influence conductivity and formability expectations. For critical electrical or thermal components, request mill certificates tied to the precise standard and consider pre-qualification testing for high-reliability parts.

Corrosion Resistance

1090 exhibits excellent atmospheric corrosion resistance due to the rapid formation of a stable, protective aluminum oxide film. In rural and urban atmospheres the alloy performs very well, and minor increases in impurity content typically do not compromise long-term surface stability unless aggressive pollutants are present.

In marine environments, 1090 has good resistance to general corrosion but is susceptible to localized attack in stagnant chloride-bearing conditions or under electrolytic coupling. When used in seawater or splash zones, design measures such as rinsing, coatings, or isolation from dissimilar metals are commonly applied to minimize pitting and crevice corrosion.

Stress-corrosion cracking is uncommon in 1090 because of its low strength and lack of susceptible precipitates; however, hydrogen embrittlement and SCC mechanisms tied to high-strength aluminum alloys are not a primary concern. Galvanic interactions are important: 1090 will act anodically relative to many stainless steels and copper alloys, so isolation or sacrificial anodes should be considered in mixed-metal assemblies.

Compared with more heavily alloyed series, the 1xxx family, including 1090, provides superior general corrosion resistance but does not offer enhanced localized corrosion resistance found in some corrosion-optimized alloys; selection should be driven by the specific service environment and joining strategy.

Fabrication Properties

Weldability

1090 welds readily with common fusion processes (TIG, MIG) and resistance welding, and it generally shows low susceptibility to hot cracking because of its purity. Use of matching or slightly higher-alloy filler materials is sometimes recommended to improve mechanical balance and reduce porosity; ER4043 or ER4047 filler wires are common choices depending on joint geometry and service requirements.

Heat-affected zones in welded 1090 do not undergo precipitate-based softening, but they can experience grain growth and local property changes; welding parameters should minimize heat input for thinner sections to reduce distortion. Pre-cleaning and flux control are important to avoid hydrogen pickup and porosity, particularly for applications requiring high electrical conductivity.

Machinability

Machining 1090 behaves similarly to pure aluminum: it is relatively easy to machine but tends toward gummy chips at high feed rates if tooling is not optimized. Recommended tooling includes sharp carbide or high-speed steel with polished flutes; higher cutting speeds and light depths of cut produce good surface finish but increase tool heat, which can cause built-up edge.

Because 1090 is soft, chip evacuation and tool geometry are critical to prevent clogging and scoring; use of coolant and positive rake angles improves performance. Machinability indices are moderate compared with free-machining alloyed grades; some manufacturers add minimal elements to improve machinability, but those changes reduce conductivity.

Formability

Formability of 1090 in the O condition is excellent: the alloy supports deep drawing, stretch forming, and complex stamping without cracking. Minimum bend radii are small in annealed material and increase as the material is hardened; for critical bends, O or H12 tempers are preferred to control springback and minimize fracture.

Cold-work response is predictable: controlled reductions yield desired tensile increases, and intermediate anneals can restore ductility for multistage forming. For severe forming operations, warm forming can be used to reduce flow stress and delay necking while maintaining surface quality.

Heat Treatment Behavior

1090 is a non-heat-treatable alloy; classical solutionizing and precipitation aging cycles are ineffective because there is insufficient alloy content to form strengthening precipitates. Therefore, property control relies on work hardening by plastic deformation and recovery/recrystallization via annealing.

Typical annealing for 1090 uses temperatures in the range of ~300–415 °C to achieve recrystallization and full softening, with soak times adjusted by thickness and section size. Partial anneals (e.g., H24-type processes) enable a controlled balance between ductility and residual strength for intermediate tempers, while full anneal (O) restores maximum formability.

Engineers should not attempt to chase higher strengths through thermal aging; instead, cold work schedules, intermediate stress relief anneals, or design changes are the appropriate levers to achieve required mechanical properties. Post-forming stabilization treatments can be used to reduce springback and minimize residual stresses.

High-Temperature Performance

1090 loses stiffness and strength progressively with temperature; at temperatures above ~100–150 °C mechanical strength declines noticeably, and elevated-temperature creep becomes relevant for sustained loads. The alloy is generally not recommended for structural service temperatures above approximately 150 °C for long durations.

Oxidation resistance at elevated temperatures is good because aluminum rapidly forms a protective oxide; however, surface scaling or color changes occur at high temperatures and can affect appearance or contact resistance. Thermal stability of mechanical properties is limited because the alloy lacks precipitate-strengthening mechanisms; hence, high-temperature hardness recovery via aging does not apply.

Heat-affected zones from welding at elevated service temperatures show little precipitation-related degradation, but grain growth and softening due to extended exposure must be considered in design. For cyclic thermal environments, differential expansion and thermal fatigue are design drivers because 1090’s high thermal expansion can induce stresses against restrained structures.

Applications

Industry	Example Component	Why 1090 Is Used
Electrical	Busbars, conductors, capacitor foils	High electrical conductivity and formability
Marine & Chemical	Tank liners, ducting, cladding	Corrosion resistance and ease of fabrication
Lighting & Reflective	Reflectors, lamp components	High reflectivity and good surface finish
Electronics & Thermal	Heat sinks, thermal spreaders	High thermal conductivity and low density
Architectural	Decorative panels, fascia	Formability, finishability, and corrosion resistance

1090 finds niche use whenever high purity, conductivity, or surface quality outweigh the need for high structural strength. Its low density and ease of forming make it cost-effective for thin-gauge applications and for components where welding and brazing are common.

Selection Insights

For applications prioritizing electrical or thermal conduction with good formability, 1090 is chosen over commercially-pure 1100 because 1090 has a higher nominal aluminum content and therefore slightly better conductivity and surface appearance, while still providing acceptable formability. The trade-off is that incremental increases in strength are limited compared with intentional alloying.

Compared with common work-hardened alloys such as 3003 or 5052, 1090 offers superior electrical and thermal performance and generally better corrosion behavior in many environments, but it delivers lower strength and less resistance to certain forms of mechanical wear. Choose 1090 when conductivity and finish trump required load-bearing capability.

Compared with heat-treatable alloys like 6061 or 6063, 1090 will never reach the peak strengths achievable by precipitation-hardening alloys, but it will outperform them in conductivity and formability and often cost less. Use 1090 when lightweight, conductive, and highly formable material is more important than maximal structural strength.

Closing Summary

1090 aluminum remains a relevant engineering choice where high electrical and thermal conductivity, excellent formability, and superior corrosion resistance at minimal cost are prioritized. Its predictable cold-work response and broad compatibility with common fabrication processes make it a reliable material for electrical, thermal, decorative, and chemical-application components.