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The selection of anti-corrosion, anti mold and sterilizing agents needs to be comprehensively judged based on multiple dimensions such as application scenarios, system chemical environment, target microbial types, formula compatibility, finished product performance impact, safety regulations and costs, and cannot be screened based solely on a single indicator of sterilization efficiency. Industrial waterborne coatings, polymer lotion, adhesives and other systems are generally divided into two categories: tank preservatives (to kill bacteria and yeasts in the system, to prevent tank odor and drum swelling) and dry film preservatives (to inhibit the growth of mold and algae on the surface of the film, and to prevent the film from mildewing and blackening). There are obvious differences in selection logic between the two.

1. Clearly define the purpose of use and distinguish between anti-corrosion and dry film mold prevention inside the tank

The preservatives in the tank mainly aim at inhibiting the propagation of bacteria and yeasts in the water phase during the product storage stage, and solving the problems of lotion and coating in the packaging barrel, such as corruption, odor, abnormal viscosity and gas production. Require fungicides to have good water solubility, be evenly dispersed in the aqueous phase, and have a fast onset of action. Typical representatives: isothiazolinones (MIT, CMIT), organic bromides, etc.

Dry film mold inhibitor is used for solid coatings after film formation to inhibit the growth of mold and algae on the surface of the paint film. Fungicides need to migrate and accumulate on the surface of the coating during film formation, with low water solubility and less likely to be washed away by rainwater. Typical representatives: Benzimidazole derivatives, Zinc Pyrithione (ZPT), Bactrobin, etc.

Attention: It is difficult for a single agent to simultaneously achieve excellent in tank anti-corrosion and long-term dry film mold prevention, so compound systems are often used in engineering.

2. Evaluate the compatibility stability with the formula system

The selection process primarily involves conducting compatibility trials to examine the compatibility of fungicides with resins, emulsifiers, dispersants, wetting agents, thickeners, and pigments within the system.

1. Charge matching: Cationic fungicides cannot coexist with anionic dispersants, wetting agents, and soaps, and will undergo chelation precipitation, leading to system instability.

2. pH adaptation range: Isothiazolinones are prone to hydrolysis and failure in environments with pH>9.5; Some organic sulfur fungicides are suitable for acidic systems, but their activity decreases under alkaline conditions.

3. Avoid oxidation-reduction reaction: oxidizing bactericide will damage lotion resin and dye, causing discoloration and degradation of finished products, and is generally not used for anti-corrosion in lotion tank.

4. Observation indicators: After addition, observe whether the system is stratified, turbid, precipitated, discolored, and has abnormal viscosity, while also testing whether the bactericidal activity is retained.

3. Target microbial species and environmental conditions

Determine the types of microorganisms that need to be inhibited based on the product’s usage environment:

Corruption inside the tank: mainly composed of Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa), accompanied by yeast;

Dry film environment: damp exterior walls, high humidity environment in basements, dominated by molds such as Aspergillus niger and Penicillium, and outdoor environments also need to consider algae.

Environmental temperature and humidity also affect the effectiveness of pesticides: for high-temperature storage systems, priority should be given to selecting fungicides with good thermal stability; For high humidity outdoor coatings, choose dry film anti mold agents that are resistant to rainwater erosion and have low water precipitation. When the hardness of the water is high, some fungicides are prone to chelation and deactivation with calcium and magnesium ions, requiring the use of chelating agents or the replacement of drug varieties.

4. Investigate the negative impact on the performance of the finished product

The final performance of coating and lotion shall not be damaged after the addition of bactericide, and it is required to verify that:

· Influence on lotion polymerization and film forming performance;

Has it caused discoloration, yellowing, or loss of gloss in the paint film;

The impact on adhesion, water resistance, and weather resistance;

Some powder anti mold agents can affect the gloss, and high gloss paints need to be carefully selected.

5. Safety, Toxicology, and Regulatory Requirements

Acute toxicity, skin irritation, and sensitization need to be evaluated, while meeting regulatory restrictions in both domestic and export regions.

Pay attention to the allowable limit of adding fungicides, such as MIT’s limit in some daily chemical and coating products;

Avoid heavy metals and persistent organic fungicides as much as possible;

At the operational level: volatility, inhalation risk, and requirements for waste liquid treatment;

Food contact and indoor paint scenes have stricter requirements for residual and release of fungicides.

6. Drug resistance prevention and control

Long term use of single mechanism fungicides alone can easily lead to the development of drug-resistant strains in microorganisms. Selection strategy: Prioritize the use of multi-target compound fungicides; Rotating use of drugs with different mechanisms; Regularly conduct microbial challenge tests to monitor the effectiveness of the anti-corrosion system.

7. Cost and Storage Stability

Taking into account both performance and usage costs, it is not only important to consider the unit price of the medication, but also to compare the effective dosage. At the same time, investigate the storage stability of the fungicide solution: whether it is easy to hydrolyze, decompose under light, precipitate at low temperatures, and meet the requirements of raw material storage and product shelf life.

8. Microbial Challenge Validation

After the preliminary selection is completed, the actual effectiveness of anti-corrosion and anti mold measures must be verified through microbial challenge tests. Simulate production pollution and repeated pollution conditions, regularly test the number of microorganisms, confirm that the selected fungicide can inhibit microbial proliferation for a long time, and conduct pilot scale testing after passing the small-scale test.