Can I Use a Lifting Slings in Acidic or Alkaline Environments?

A chemical processing plant needs to lift stainless steel reactor components in an area where acid vapors are present. A concrete manufacturer needs to move formwork in an environment exposed to alkaline solutions. Both operations require lifting slings—but the right material for each is completely different.

Using nylon in an acid environment or polyester in an alkaline environment can cause invisible strength loss that leads to catastrophic failure. Lishenflex has been manufacturing synthetic lifting slings for decades, and our experience shows that chemical compatibility is one of the most overlooked—and most dangerous—factors in sling selection. Unlike mechanical damage such as cuts or abrasion, chemical degradation often leaves no visible trace until the sling fails under load.

1. The Fundamental Rule: Nylon vs. Polyester

The chemical resistance of synthetic lifting slings follows a clear rule that every rigger and safety professional must know.

1.1 Nylon Slings: Resistant to Alkalis, Damaged by Acids

According to the Canadian Centre for Occupational Health and Safety (CCOHS), nylon slings are damaged by acids but resist alkalis. The NSRP Ship Production Rigging Guide provides more specific detail: hydrochloric acids and sulfuric acids, even in diluted form, can cause significant loss of strength in nylon. Some chemicals that act as solvents for nylon include formic acid, phenolic compounds, calcium chloride, zinc chloride, and benzyl alcohol.

The Washington Administrative Code (WAC 296-24-29431) specifically prohibits the use of nylon web slings where fumes, vapors, sprays, mists, or liquids of acids or phenolics are present. This is a regulatory requirement, not just a recommendation.

1.2 Polyester Slings: Resistant to Acids, Damaged by Alkalis

Polyester exhibits the opposite chemical profile. According to CCOHS, polyester slings are damaged by alkalis but resist acids. The NSRP guide notes that polyester is resistant to aqueous solutions and strong alkalis at room temperatures, but when brought to boil, these substances will destroy the material. Concentrated sulfuric acid causes polyester to disintegrate.

Mennens product specifications confirm that polyester slings are “resistant to most acids but not to strong alkalis”. Mazzella Companies adds that polyester is subject to degradation in alkalis “ranging from none to total degradation,” and the specific effect depends on the type of alkali, concentration, temperature, and exposure duration.

1.3 The Practical Implication

Source: CCOHS; NSRP Ship Production Rigging Guide; WAC 296-24-29431

Lishenflex's field data confirm that slings used in chemically active environments without proper material matching can lose 30–50% of their rated strength within weeks, often without any visible surface change. This is why understanding the material-environment compatibility is not optional—it is essential.

2. Warning Signs of Chemical Damage

Chemical damage to lifting slings is often invisible until failure. However, certain visual and tactile indicators can signal that a sling has been compromised.

2.1 Visual Indicators

Per ASME B30.9, the following conditions require immediate removal from service:

• Acid or caustic burns—visible burns or discoloration

• Discoloration—unusual color changes, often brown, black, or patchy

• Melting or charring—though this may also indicate heat damage

The NSRP guide warns that chemically damaged slings often appear stiff and brittle, and may develop a brown or black discoloration even without visible liquid contact. Chemical fumes and vapors can cause degradation just as effectively as direct liquid exposure.

2.2 Tactile Indicators

• Increased stiffness—the webbing feels rigid or board-like

• Brittle fibers—fibers break easily when bent

• Hard or crunchy texture—may indicate chemical damage similar to heat damage

CCOHS specifically lists “increased stiffness of sling material” as a sign of chemical damage that makes a sling unusable. If a sling that was previously flexible becomes stiff or hard, it should be removed from service immediately.

3. Standards and Regulations

3.1 ASME B30.9 Removal Criteria

ASME B30.9 specifies that a synthetic web sling shall be removed from service if any of the following conditions are present:

• Acid or caustic burns

• Discoloration and brittle or stiff areas which may indicate chemical or ultraviolet/sunlight damage

• Melting or charring of any part of the sling

These criteria apply regardless of whether the damage is visible on the surface or suspected internally.

3.2 OSHA and WAC Requirements

WAC 296-24-29431 (adopted under OSHA) specifically requires that nylon web slings shall not be used where fumes, vapors, sprays, mists, or liquids of acids or phenolics are present. This is a mandatory prohibition, not a recommendation.

OSHA 1915.112 and general industry standards require that slings be inspected for chemical damage before each use, and that damaged slings be removed from service immediately.

3.3 Manufacturer Guidance

Mazzella Companies advises that chemically active environments can affect synthetic web slings “in varying degrees ranging from none to total degradation,” and recommends consulting the sling manufacturer before using slings in chemically active environments.

Olsen Chain and Cable notes that chemicals such as acids or alkalis and ultraviolet light can affect the strength of synthetic web slings, and that chemically active environments (liquids, solids, vapors or fumes) can degrade strength.

4. Best Practices for Chemically Active Environments

4.1 Material Selection

• For acid environments: Choose polyester slings. They resist most acids, including hydrochloric and sulfuric acid in dilute form.

• For alkaline environments: Choose nylon slings. They resist alkalis where polyester would degrade.

• For mixed or unknown environments: Consult the sling manufacturer with specific chemical information (type, concentration, temperature).

4.2 Protective Measures

• Use protective sleeves: Polyurethane or neoprene coatings can provide an additional barrier against chemical exposure.

• Avoid direct contact: Whenever possible, keep slings away from chemical spills, fumes, and vapors.

• Inspect frequently: In chemically active environments, inspect slings before every use and perform periodic inspections more frequently than in normal service.

4.3 Storage

Mazzella Companies recommends storing slings in a cool, dry, and dark place, away from ultraviolet light and chemical exposure. Slings should never be stored in areas where chemical fumes or vapors are present.

5. Summary and Practical Recommendations

The question “Can I use a lifting sling in acidic or alkaline environments?” has a clear answer: It depends on the material.

• Nylon is damaged by acids but resists alkalis.

• Polyester is damaged by alkalis but resists acids.

Using the wrong material can cause invisible strength loss, sudden failure, and safety hazards. According to ASME B30.9, any sling showing signs of chemical damage—discoloration, stiffness, brittleness, or burns—must be removed from service immediately.

Key takeaways:

1. Match material to environment—polyester for acids, nylon for alkalis

2. Inspect for hidden damage—stiffness and discoloration indicate chemical degradation

3. Follow regulatory requirements—WAC 296-24-29431 prohibits nylon in acid environments

4. Protect slings—use sleeves, avoid direct contact, store properly

5. When in doubt, consult the manufacturer—chemical environments vary widely in concentration and temperature

Lishenflex manufactures both polyester and nylon lifting slings to EN 1492-1 and ASME B30.9 standards, with clear material identification and color-coded capacity markings. We offer guidance on material selection for chemically active environments and can provide protective sleeve options for additional chemical resistance.

If you need assistance selecting the right lifting sling for your chemically active environment—or need help determining whether your current slings are suitable for the chemicals they are exposed to—please send an email to sales@lishenflex.com, and our technical team will provide one-on-one support.