Direct answer

Both materials can be suitable; the best choice depends on the environment, weight requirements, cost, and maintenance needs. OSHA’s fixed ladder criteria are written the same way: 1910.23(b)(6) requires that metal ladders be made with corrosion-resistant material or be protected against corrosion, and it stops there; OSHA does not prefer aluminum over galvanized steel, or the reverse.¹ Either material, properly specified, satisfies that requirement, so the practical differences between them are weight, maintenance and long-term corrosion performance rather than code compliance.

6061-T6 aluminum weighs roughly half as much as galvanized steel for a comparable ladder, and its corrosion protection is a passive oxide film that forms on the metal itself rather than a coating applied to it, so it generally requires less maintenance in coastal or otherwise corrosive environments. Galvanized steel typically costs less upfront and offers higher strength and stiffness in a compact section, but its zinc coating protects the steel sacrificially and is consumed in the process, which gives the coating a finite life and can call for touch-up once it is damaged.

Neither material is universally correct, so the choice usually comes down to project-specific factors, exposure severity, weight limitations on the supporting structure, budget and expected maintenance capacity, rather than a default assumption that one material is superior for every application.

What OSHA’s material requirement actually says

OSHA’s fixed ladder standard does not specify a required material; it requires that a ladder and its component parts be constructed of corrosion-resistant material, or be treated to prevent corrosion, and be substantially constructed to withstand its intended load.¹ Both properly specified 6061-T6 aluminum and properly galvanized steel can satisfy this requirement, meaning the material decision is more a matter of project-specific performance and cost tradeoffs than a compliance question with a single correct answer.

Weight and structural differences

Aluminum’s lower density gives it a clear weight advantage: a comparable ladder section in 6061-T6 aluminum can weigh roughly half what the same section weighs in galvanized steel.² The difference in weight can affect the supporting structure’s load capacity, ease of field handling and installation, and shipping costs. Galvanized steel’s greater mass and higher strength and stiffness in a given compact section can be advantageous where maximum rigidity is the priority.

Alaco Ladder’s heavy-duty aluminum ladder line is designed to address these structural requirements by using heavier-gauge aluminum components rather than switching to steel.

Corrosion protection mechanism differences

The two materials both resist corrosion, but they do it by opposite mechanisms, and the difference shows up in maintenance and service life rather than on the day the ladder is installed.

Aluminum protects itself with a passive oxide film. On exposure to air, the surface of the alloy reacts to form a thin, tightly adhering layer of aluminum oxide that separates the metal beneath it from the atmosphere. That film is not consumed as it does its job, and it re-forms on any freshly exposed aluminum, so a rail that is scratched during handling, gouged at an anchor location or cut in the field is oxidized over again within a short time and is protected without coating work.² For a specifier, that means no scheduled recoating and no coating thickness to track as it diminishes. It does not mean aluminum is inert: it remains vulnerable to galvanic attack where it is coupled directly to dissimilar metals, and to pitting where chlorides stand on the surface, so isolation at steel connections and drainage at horizontal surfaces still belong in the detail.

Galvanized steel is protected sacrificially by its zinc. Hot-dip galvanizing to ASTM A123 leaves a zinc coating that acts first as a barrier and, more importantly, as an anode: zinc is less noble than steel, so where moisture reaches the two together, the zinc corrodes preferentially and the steel underneath does not.³ This is why a scratch in a galvanized surface is not an immediate failure; the zinc surrounding the scratch continues to protect the small area of exposed steel. The protection is real, but it is paid for out of the coating. Zinc that has protected a scratch is zinc that is no longer there, and coating thickness declines over the ladder’s life at a rate set by the severity of the exposure, faster in coastal, industrial or de-icing-salt environments than in dry inland air. Where the coating has been breached to bare steel over an area larger than the surrounding zinc can cover, or where measured thickness has dropped, the remedy is field repair with a zinc-rich compound applied to the coating specification.³

The practical consequence is a difference in maintenance model, not in whether the ladder is protected. Aluminum’s protection regenerates, so the owner’s obligation is closer to inspection than upkeep. Galvanized steel’s protection is a consumable with a definable life, so the maintenance program has to include periodic coating inspection, touch-up of field damage, and an expectation that the coating will eventually need renewal in aggressive exposures.

Cost and maintenance over the service life

Galvanized steel typically has a lower upfront material cost and a widely available hot-dip galvanizing supply chain, while aluminum’s higher unit cost is often offset over the ladder’s service life by lower maintenance, since a damaged galvanized coating needs to be repaired to maintain its corrosion protection while aluminum’s self-forming oxide layer does not.² The comparison shifts depending on how a project weighs upfront capital cost against total cost of ownership over the structure’s expected service life.

When one material is typically preferred over the other

For a custom-engineered ladder, 6061-T6 aluminum extruded to standard structural profiles under ASTM B308 is a common choice where weight, corrosion resistance and low maintenance are priorities, such as coastal sites or ladders mounted on structures with limited load capacity.⁴ Galvanized steel tends to be preferred where strength and stiffness in a compact section, higher point loads, or a lower upfront material cost matter more than long-term maintenance.

Alaco Ladder’s aluminum ladders vs. steel ladders page compares these tradeoffs directly for a fixed access ladder application.

What to ask a manufacturer about material selection

• What is driving the material decision on this project: weight, corrosion exposure, cost, or supporting structure capacity?
• If aluminum, is the alloy and temper 6061-T6, and does it conform to a recognized structural profile standard?
• If galvanized steel, is the coating applied and inspected to ASTM A123, and what is the touch-up procedure for field damage?
• What is the manufacturer’s estimate of long-term maintenance cost for each material option at this site?

Key takeaway

6061-T6 aluminum and galvanized steel can both meet OSHA’s fixed ladder material requirements, so the choice between them is a project-specific tradeoff rather than a compliance question. Aluminum generally offers lower weight and lower long-term maintenance because its protective oxide film re-forms on its own, while galvanized steel generally offers a lower upfront cost and higher strength and stiffness in a compact section, with a zinc coating that is consumed as it protects the steel.

Matching the material to the site’s exposure, the supporting structure’s capacity and the owner’s maintenance expectations is more useful than defaulting to either material as a universal standard.

Glossary

• 6061-T6: An aluminum alloy and temper combination commonly used in structural applications for its balance of strength, corrosion resistance and weldability.
• Hot-dip galvanizing: A process of coating steel with zinc by immersion in a molten zinc bath to provide sacrificial corrosion protection.
• Passive oxide film: The thin, self-forming layer of aluminum oxide that develops on an aluminum surface exposed to air, protecting the metal beneath without being consumed and re-forming where the surface is damaged.
• Sacrificial coating: A protective coating, such as zinc on steel, that corrodes preferentially to protect the base metal beneath it.
• Structural profile: A standardized cross-sectional shape, such as an angle, channel or tee, produced to a recognized material specification.
• Total cost of ownership: The combined upfront and lifecycle cost of a material or product, including maintenance and repair over its service life.

References

1. “1910.23 – Ladders.” Occupational Safety and Health Administration. Accessed August 6, 2026. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.23/.
2. “Hot-Dip Galvanized vs. Aluminum.” Cable Tray Institute. Accessed August 6, 2026. https://www.cabletrays.org/hot-dip-galvanized-vs-aluminum/.
3. “Overview of ASTM A123/A123M.” American Galvanizers Association. Accessed August 6, 2026. https://galvanizeit.org/knowledgebase/article/astm-a123-a123m/.
4. “B308/B308M Standard Specification for Aluminum-Alloy 6061-T6 Standard Structural Profiles.” ASTM International. 2020. Accessed August 6, 2026. https://store.astm.org/b0308_b0308m-20.html.