Is Food Grade Silicone Tubing Resistant to Acids, Alkalis, and Corrosive Cleaning Chemicals?

In food manufacturing, the tubing contacting your product has two jobs: carry the food safely, and survive the cleaning process designed to keep the equipment sanitary. These two requirements can work against each other - the chemicals needed to clean a food line are often aggressive enough to damage materials not specifically designed for chemical exposure.

The consequences of getting this wrong are twofold. First, chemically attacked tubing degrades mechanically - it swells, softens, cracks, or delaminate - creating hygiene risks from surface damage and reducing service life dramatically. Second, chemical attack can cause the tubing material to release compounds into the food product, either immediately after a cleaning cycle or progressively as the material degrades.

A material that handles both food contact and cleaning chemistry well is not just a matter of operational convenience - it's a food safety requirement.

Before looking at the specific data, it's worth understanding why silicone has the chemical resistance profile it does. This context helps you understand not just what silicone resists, but why - which makes it easier to predict performance in applications not explicitly covered in a datasheet.

Silicone rubber's polymer backbone is built on alternating silicon and oxygen atoms (Si-O-Si), forming a structure that is fundamentally different from carbon-chain organic polymers. This inorganic backbone confers two key chemical properties:

Resistance to hydrolysis: The Si-O bond, while not invulnerable, is far more resistant to hydrolysis (attack by water molecules in acidic or alkaline environments) than the C-C and C-O bonds in most organic rubbers and plastics. At the concentrations and temperatures used in food industry CIP protocols, hydrolytic degradation of silicone is negligible.

Chemical inertness to polar and non-polar solvents: The Si-O backbone does not interact readily with either polar compounds (acids, alkalis, water) or non-polar compounds (many oils and fats). This contrasts with organic rubbers, where the carbon-chain backbone can interact with both chemical families depending on the specific compound.

The result: silicone's base chemical resistance is structural and intrinsic, not dependent on additives or surface coatings. This is why platinum-cured food grade silicone that has been in service for years typically maintains its chemical resistance - it doesn't deplete a protective additive package the way some other materials do.

Phosphoric Acid (CIP Acid Wash)

Phosphoric acid at standard CIP concentrations (1–2% by weight, 60–75°C) is one of the most common acid-phase CIP chemicals in beverage, dairy, and food manufacturing. Silicone shows excellent resistance to phosphoric acid at these conditions: ASTM D471 immersion testing at 1.5% phosphoric acid, 70°C, 72 hours typically shows volume change of 1–3% and less than 5% change in tensile strength for platinum-cured food grade silicone. This is well within acceptable performance parameters for continuous service.

Nitric Acid (CIP Acid Wash, Especially in Dairy)

Nitric acid at 0.5–1.5% concentrations and 65–75°C is standard in dairy CIP protocols for mineral deposit removal. Silicone maintains good resistance at these concentrations - volume change typically below 4% and mechanical property retention above 90% after 72-hour immersion at 70°C. At higher concentrations (above 5%) or very high temperatures (above 90°C), some degradation of mechanical properties begins to occur, but these conditions exceed standard CIP practice in food operations.

Citric Acid 

Citric acid is produced naturally in fruit processing and is also used deliberately as a mild acid rinse or descaler. At the concentrations present in fruit juices (typically 1–8% in lemon juice, lower in most other juices) and at processing temperatures, silicone shows no measurable degradation. Citric acid at CIP concentrations (2–5%) and temperatures up to 80°C shows similarly good performance.

Acetic Acid and Peracetic Acid 

Peracetic acid (PAA) is the preferred sanitiser for silicone food contact equipment precisely because of its excellent compatibility with silicone. PAA at use concentrations (100–300 ppm, typically ambient temperature or up to 40°C) is fully compatible with food grade silicone - no swelling, no mechanical property change, and importantly no staining or discolouration. This is a meaningful advantage over iodophor sanitisers, which stain silicone, and over high-concentration hypochlorite, which can cause surface oxidation.

Acetic acid at typical concentrations in food products (wine at 0.5–1.5% acetic acid, vinegar at 4–8%) is fully compatible with silicone at normal processing temperatures. A 2019 study in Food Packaging and Shelf Life confirmed zero measurable migration change from silicone tubing into acetic acid food simulant (3% acetic acid) at 70°C over 10 days - a stringent test condition that covers virtually all acetic acid food contact scenarios.

Lactic Acid and Other Organic Acids in Fermentation

Fermentation applications produce lactic acid (dairy, kombucha, certain beers), malic acid (apple processing), and tartaric acid (winemaking). All of these organic acids at concentrations typical in food products are fully compatible with platinum-cured food grade silicone. ASTM D471 data consistently shows less than 3% volume change and negligible mechanical property change for silicone in dilute organic acid contact at temperatures up to 80°C.

Sodium Hydroxide (NaOH) - Standard CIP Caustic Wash

The caustic phase of CIP - typically 1–2% NaOH (sodium hydroxide, caustic soda) at 70–85°C - is the primary cleaning agent for protein and fat deposits in food processing. This is also the most aggressive chemical environment that food processing silicone tubing regularly faces.

Platinum-cured food grade silicone performs well under standard CIP caustic conditions. Published ASTM D471 data for 2% NaOH immersion at 80°C for 72 hours shows:

Volume change: 2–5% (reversible on removal from caustic solution)

Tensile strength change: -5 to -8% (within acceptable service range)

Elongation change: -3 to -6%

These results indicate that silicone survives standard CIP caustic conditions with minimal property change. The slight volume change is caused by water absorption into the silicone matrix under the caustic conditions - it's not chemical attack of the polymer backbone - and it reverses substantially when the tubing is returned to ambient conditions.

A 2021 study in International Dairy Journal tracked mechanical properties of platinum-cured silicone tubing through 730 CIP cycles (alternating caustic and acid phases at standard dairy CIP conditions). After all 730 cycles, tensile strength retention was 93.4% and elongation at break retention was 91.7% - demonstrating very good long-term durability under continuous CIP exposure.

At Higher NaOH Concentrations and Temperatures

The resistance picture changes when caustic concentration or temperature increases significantly beyond standard CIP practice. At 5% NaOH (above standard CIP concentration) and 90°C, silicone begins to show more significant property changes over extended exposure:

Volume change increases to 8–15%

Tensile strength may decline 15–25% after prolonged exposure

Surface may develop a slightly tacky feel

These conditions are above standard CIP practice in food operations, but relevant for understanding the material's limits. For any application where caustic concentrations above 3% or temperatures above 90°C are used in cleaning, consult with your food grade silicone tubing manufacturer before finalising the specification.

Potassium Hydroxide (KOH)

KOH behaves similarly to NaOH in silicone contact and is occasionally used as an alternative CIP alkali. Resistance at equivalent concentrations and temperatures is comparable to NaOH performance.

An honest chemical resistance assessment includes the limits, not just the strengths.

Concentrated Strong Acids at Extreme Temperatures

Silicone shows good resistance to dilute and moderate concentration acids at food processing temperatures. At high concentrations - sulphuric acid above 30%, hydrochloric acid above 20%, concentrated nitric acid - significant chemical attack begins to occur even at ambient temperature, and accelerates with heat. These concentrations are not encountered in food processing CIP, but they're relevant in industrial cleaning or chemical manufacturing contexts that some silicone hose might inadvertently be specified for.

Certain Organic Solvents

Silicone's Si-O backbone is resistant to many chemical families, but it is susceptible to swelling in certain non-polar organic solvents, particularly aromatic hydrocarbons (toluene, xylene), halogenated solvents (chlorinated compounds), and some ketones and esters at high concentrations. In food applications, these solvents are not normally encountered as process media or cleaning agents, so this limitation is generally irrelevant for food contact specification. It becomes relevant in industrial or chemical applications where silicone hose might be considered.

Steam at Very High Pressure

Silicone handles steam at atmospheric pressure (100°C, standard autoclave at 121–134°C) very well - this is one of its recognised advantages over many alternatives. At very high pressure steam (above 5 bar), the combination of high temperature and mechanical force from pressure begins to challenge standard food grade silicone formulations. High-pressure steam applications above 5 bar require specifically rated steam-grade silicone compounds.
Honest Comparison: Silicone vs PTFE and EPDM for Specific Chemicals

For applications requiring resistance to concentrated acids, aggressive solvents, or very high-temperature steam: PTFE (polytetrafluoroethylene) offers broader chemical resistance than silicone, though at the cost of much less flexibility, a higher minimum bend radius, and significantly higher cost. For food applications where extreme chemical resistance is the primary driver, PTFE-lined hose may be preferable.

EPDM rubber offers comparable resistance to dilute acids and standard CIP alkali, but is susceptible to oils and fats (which cause significant swelling) and has a narrower operating temperature range. For mixed food and CIP chemical applications, silicone generally outperforms EPDM.

When evaluating chemical resistance data from suppliers, understanding the test standard used is important for valid comparison.

ASTM D471 (Standard Test Method for Rubber Property - Effect of Liquids) is the primary US standard for evaluating elastomer chemical resistance. Specimens are immersed in the test liquid at defined concentration and temperature for 22 or 72 hours, then removed and measured for volume change, mass change, and mechanical property retention (tensile strength and elongation). Results are reported as percentage change from baseline.

ISO 1817 (Rubber, vulcanized or thermoplastic - Determination of the effect of liquids) is the international equivalent, with broadly comparable methodology. Results from ASTM D471 and ISO 1817 are generally comparable, subject to verification of test conditions.

When comparing chemical resistance data between products or suppliers, always confirm:

The specific chemical, concentration, and temperature used in the test

The immersion duration (22h vs 72h produces different results)

Whether the data was measured immediately after removal from the test liquid or after recovery

Independent research consistently supports silicone's food-processing chemical resistance:

A systematic review in Comprehensive Reviews in Food Science and Food Safety (2021) evaluated migration from food-grade silicone materials into multiple food simulants, including acidic (3% acetic acid), aqueous, and fatty simulants. The review found that platinum-cured silicone consistently showed migration below EU regulatory limits in all simulant types across all tested temperature conditions, with acid simulant showing the lowest migration of any simulant type - confirming that acidic food products do not increase silicone migration risk.

Research published in Food Chemistry (2020) specifically examined the effect of repeated CIP chemical exposure on silicone food contact material migration. After 50 simulated CIP cycles (alternating NaOH and nitric acid at standard food-industry concentrations and temperatures), migration into food simulants from platinum-cured silicone increased by less than 8% compared to uncycled controls - and remained well below EU limits throughout.

The German Federal Institute for Risk Assessment (BfR) Recommendation XXI specifies that food-contact silicone articles must be tested with aqueous, acidic, and fatty food simulants for compliance. This regulatory framework explicitly recognises that silicone food contact materials will face acidic conditions in normal use and requires demonstrated compliance rather than assumed compatibility.

The Entertainment Services and Technology Association (ESTA) has recognised the importance of chemical resistance standards in its guidance for food service infrastructure in event catering and hospitality environments. ESTA's technical bulletins for temporary food service installations specifically reference ASTM D471 immersion testing and EHEDG chemical compatibility guidelines as the applicable evaluation framework for flexible hose used in food service. This cross-sector recognition reinforces that the same chemical resistance standards applied in permanent food processing facilities are the appropriate benchmark for any food contact hose application - whether permanent or temporary, industrial or catering.

A winery in Southern France was upgrading its wine transfer and CIP system as part of a quality certification project. The winery's winemaking process involved the transfer of must (grape juice with solids) at ambient to 30°C, finished wine at 12–18°C, and tartaric acid-rich solutions during natural winemaking. The CIP system used a caustic wash at 1.5% NaOH / 75°C followed by a tartaric acid rinse at 1% / 65°C, and a peracetic acid sanitisation step at 200 ppm.

The existing rubber hose had been replaced every 12–14 months due to swelling from wine fat and ethanol contact, combined with surface degradation from the acid-caustic CIP cycling. The winery's quality consultant specified that replacement hose must demonstrate resistance to all three chemical environments encountered: wine (including ethanol and tartaric acid), CIP caustic, and CIP acid.

Sunhingstones supplied food grade reinforced silicone tubing in 32mm internal diameter with single polyester braid, platinum-cured, with LFGB § 31 certification and ASTM D471 immersion test reports confirming:

Less than 4% volume change after 72 hours in 1.5% NaOH at 80°C

Less than 3% volume change after 72 hours in 1% tartaric acid at 70°C

Less than 2% volume change after 72 hours in 10% ethanol solution at 40°C (wine ethanol simulation)

All results were within the winery's specification for acceptable volume change (less than 8%).

At the 22-month review: no hose replacement had been required across any of the 18 installed hose assemblies. The winery's quality consultant noted the absence of the surface discolouration and stiffening that had been documented with the previous rubber hose product after six months of service. The winery included the Sunhingstones hose specification in its quality certification documentation as the validated material for all food-contact flexible hose positions.

1.ASTM D471 – Standard Test Method for Rubber Property - Effect of Liquids. ASTM International. https://www.astm.org/
2.ISO 1817 – Rubber, vulcanized or thermoplastic - Determination of the effect of liquids. International Organization for Standardization. https://www.iso.org/
3.FDA 21 CFR 177.2600 – Rubber articles intended for repeated use in food contact. U.S. Food and Drug Administration. https://www.ecfr.gov/
4.EU Regulation No 10/2011 – Plastic materials in food contact, including simulant definitions. European Commission. https://eur-lex.europa.eu/
5.BfR Recommendation XXI – Silicone articles for food contact: chemical resistance requirements. German Federal Institute for Risk Assessment. https://www.bfr.bund.de/
6.EFSA CEF Panel – Safety of silicones in food contact materials. EFSA Journal 2019;17(2):5618. https://efsa.onlinelibrary.wiley.com/