As hygiene-control requirements in food processing become increasingly stringent, some companies are reassessing their existing disinfection systems based on production processes, water quality conditions, and sanitation objectives.

Chlorine dioxide and free chlorine follow different reaction pathways. Under suitable conditions, chlorine dioxide can reduce the formation of certain typical halogenated organic disinfection by-products and may also be used for the control of some microorganisms and biofilms. However, chlorine dioxide is not a “zero by-product” technology; chlorite, chlorate, and other related transformation products still need to be considered.

By comparison, sodium hypochlorite remains a widely used disinfectant in the food-processing industry. However, its active chlorine species and disinfection performance are more strongly affected by pH, so corresponding process control is required under different water quality, temperature, and operating conditions.

Therefore, for a food plant that has used sodium hypochlorite for many years and is considering switching to chlorine dioxide, the real issue is not simply “changing the chemical.” The plant must reassess its cleaning procedures, disinfection parameters, material compatibility, and equipment operating conditions.

The following sections look at the key points that should be verified before converting a food-processing line from sodium hypochlorite to chlorine dioxide.

I. Food Processing Is Not as Simple as “Changing the Disinfectant”

Although both chlorine dioxide and sodium hypochlorite can be used in food-processing hygiene management, their chemical characteristics, mechanisms of action, and process-control priorities are not identical.

The actual disinfection performance and material-corrosion risk of a sodium hypochlorite system are jointly affected by factors such as pH, available chlorine concentration, temperature, contact time, and material type.

Under suitable conditions, sodium hypochlorite can still provide stable disinfection performance. It should therefore not simply be regarded as “unsuitable for food plants” or as an obsolete technology.

Chlorine dioxide, on the other hand, exists mainly in molecular form and participates in selective oxidation reactions. Its disinfection performance is relatively less affected by changes in pH, and it has strong oxidation and disinfection capabilities.

However, one point must be made clear:

Strong oxidation capacity does not mean that practical disinfection performance can be expressed as a simple multiple.

The actual antimicrobial performance of chlorine dioxide still depends on:

concentration;

contact time;

temperature;

water quality;

organic load;

target microorganisms;

and the condition of equipment surfaces.

When adequate cleaning has been completed and appropriate concentration and contact time are used, chlorine dioxide can help reduce microbial loads on some equipment surfaces and within piping systems, and it can assist in biofilm control.

But it cannot provide a “one-time treatment with no recurrence.”

If food residues, proteins, fats, or other organic contaminants remain inside equipment, biofilms may re-form.

Therefore, one basic principle should always be clear in food-processing sanitation:

Effective cleaning is the foundation of effective disinfection. A disinfectant cannot replace thorough cleaning.

At the same time, although chlorine dioxide may offer process advantages for certain disinfection objectives, it is still a strong oxidizing agent. Its process advantages should not be interpreted as meaning that it is gentler on every material.

Switching from sodium hypochlorite to chlorine dioxide is therefore a systematic adjustment involving sanitation procedures, material compatibility, operating parameters, and maintenance practices.

II. Correct Material Selection Is Essential for Long-Term Operation

On food-processing lines, metal piping, seals, pumps, valves, sight glasses, spray balls, and wetted instrument components are all areas that should be carefully reviewed after changing the disinfection system.

Material compatibility with chlorine dioxide should not be reduced to a simple “compatible” or “incompatible” judgment. It should be evaluated based on:

chlorine dioxide concentration;

temperature;

contact time;

pH;

chloride concentration;

mechanical stress;

material grade;

weld quality;

and surface-treatment condition.

Figure 1. Inspection of Production-Line Materials and Piping (Illustration)

1. Metal Piping: 304 and 316L Stainless Steel Should Not Be Judged in Absolute Terms

Both 304 and 316L stainless steel are widely used in food-processing equipment.

304 stainless steel generally does not contain molybdenum, while 316L does. As a result, 316L generally has better resistance to pitting and crevice corrosion under certain chloride-containing conditions.

However, this does not mean that:

304 stainless steel can never be used with chlorine dioxide;

nor does it mean that:

316L is completely immune to corrosion at every chlorine dioxide concentration, temperature, and exposure duration.

In practice, the resistance of both materials can vary with chlorine dioxide concentration, water temperature, contact time, water chemistry, weld quality, and passivation condition.

Welds, dead zones, low-flow areas, and locations where chlorides may concentrate deserve particular attention.

Before making a full conversion, the existing 304 or 316L components should therefore be evaluated based on the actual operating conditions and material-compatibility data provided by the material supplier, rather than being replaced automatically.

A sound material assessment can help reduce the risk of pitting, crevice corrosion, leakage, and premature failure, thereby improving long-term production-line reliability.

2. Seals and Gaskets: Small Components Can Determine System Reliability

Although seals and gaskets occupy only a small part of the overall production line, their function is critical.

They not only provide equipment connections and sealing, but may also be exposed repeatedly to:

process water;

cleaning solutions;

acidic or alkaline CIP solutions;

disinfectants;

and food residues.

If material compatibility is inadequate, the following problems may occur:

swelling;

hardening;

cracking;

loss of elasticity;

seal failure;

and leakage.

PTFE and certain grades of fluoroelastomers generally have good chemical resistance and may therefore offer advantages in some strong-oxidant applications.

However, no sealing material is “naturally immune” to oxidizing agents.

Different fluoroelastomer grades, filler formulations, and seal structures may perform differently.

Compatibility should therefore be confirmed according to the specific material grade, chlorine dioxide concentration, temperature, and actual mode of use.

Proper material selection can help reduce the risk of seal aging, leakage, and frequent maintenance, but it cannot replace routine inspection and preventive replacement.

Figure 2. Selection of Seals, Gaskets, and Connection Components (Illustration)

3. Sight Glasses, Spray Balls, and Other Components: Critical Areas That Are Often Overlooked

In addition to piping and sealing components, food plants contain many wetted parts that can easily be overlooked.

Examples include:

mechanical seals in CIP centrifugal pumps;

tank sight glasses;

spray balls;

valves;

instrument probes;

wetted flowmeter components;

hoses and connectors.

After changing the disinfection system, these components should also be checked for compatibility with the actual chlorine dioxide concentration, temperature, and contact time.

Mechanical seals, sight-glass gaskets, and small valve components deserve particular attention. Once these components age or begin to leak, they can directly affect CIP integrity and production continuity.

Therefore, the main piping system should not be the only focus. Components with a small surface area but a high failure impact must also be included in the compatibility assessment.

III. A Three-Step Approach for a Smooth Transition

When a food plant changes from an existing disinfection process to chlorine dioxide, immediate full-line implementation is not recommended.

A more controlled approach is to verify actual suitability step by step through material documentation, simulated operating-condition testing, and limited-scale trial operation.

It is also important to distinguish between different application scenarios.

Chlorine dioxide may be used for:

process water;

CIP systems;

utensils and tools;

food-contact surfaces;

non-food-contact environmental surfaces;

piping and storage tanks.

The required concentration, contact time, residual-control requirements, and subsequent rinsing requirements may differ among these applications.

Therefore, actual operating parameters should be determined according to the specific product instructions, applicable standards, and validated sanitation procedures of the plant. Different application scenarios should not simply use the same disinfection parameters.

Figure 3. Material Immersion Testing and Limited-Scale Trial Operation (Illustration)

Step 1: Establish a Material Database

First, identify and record all equipment components that may come into contact with chlorine dioxide solution.

A material checklist should include, where applicable:

equipment name;

component location;

material grade;

seal material;

weld condition;

operating temperature;

expected chlorine dioxide concentration;

contact time;

historical failure records.

A traceable material database provides a technical basis for future maintenance, abnormal-condition investigation, and process optimization.

Step 2: Conduct Simulated Operating-Condition Compatibility Testing

For metal, rubber, plastic, or sealing materials whose compatibility is uncertain, testing can be performed under conditions that simulate actual operation.

The test should not be universally fixed at “72 hours of immersion.”

A more appropriate approach is to design test conditions according to the actual process, including:

actual chlorine dioxide concentration;

actual or accelerated temperature;

single-exposure duration;

frequency of use;

whether chlorine dioxide is alternated with acidic or alkaline CIP procedures;

static immersion or circulating-flow conditions.

Before and after testing, the following parameters may be compared:

mass change;

dimensional change;

surface condition;

hardness;

elasticity;

tensile properties;

sealing performance;

metal-surface corrosion.

The results can then be compared with material-supplier technical data, equipment-manufacturer requirements, or internal acceptance criteria to provide a more direct assessment of material compatibility under actual operating conditions.

Step 3: Conduct Limited-Scale Trial Operation and Establish an Inspection Program

After preliminary material verification, a limited production line, individual equipment set, or non-critical process section can be selected for staged trial operation.

It is not necessary to define a universal rule such as “one month of trial operation.” The trial period should be determined according to the production cycle, disinfection frequency, and risk level.

During trial operation, evaluation should not be limited to whether leakage or unusual odor occurs.

The plant should also monitor:

equipment material condition;

changes in seals;

actual chlorine dioxide concentration and residual;

microbiological control performance;

product-quality changes;

CIP effectiveness;

relevant residual indicators where necessary;

equipment operating stability.

Only after these key indicators meet the plant’s predefined validation criteria should the use of chlorine dioxide be gradually expanded.

A regular inspection program should also be established, with particular attention to:

welds;

sealing rings;

mechanical seals;

valves;

sight glasses;

spray balls;

hoses;

instrument probes and other high-risk components.

The earlier material degradation or operational abnormalities are identified, the easier it is to make adjustments before production is interrupted.

Switching a food-processing plant to a chlorine dioxide disinfection system is not simply a matter of replacing one chemical with another.

It involves:

cleaning procedures;

disinfection parameters;

material compatibility;

equipment condition;

residual control;

sanitation validation;

operation and maintenance.

A more reliable transition pathway is:

Establish a material database first, then conduct simulated operating-condition testing, and finally expand application step by step through limited-scale trial operation and sanitation-performance validation.

If the preliminary validation is adequate, chlorine dioxide can serve as one technical option within a food-processing sanitation-control system.

However, whether it is suitable for a specific production line should still be determined according to the food category, production equipment, cleaning method, water quality, and sanitation objectives, rather than assuming that switching to chlorine dioxide will automatically make the process safer, less costly, or less corrosive.

XIUBA can provide chlorine dioxide products, supporting equipment, and technical support for different food-processing applications, and can assist customers in evaluating disinfection parameters and material compatibility according to actual site conditions.

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