How to Choose Isothiazolinone Preservatives?

A water-based paint can spoil inside a sealed pail and still develop mold after it has been applied to a wall. These are two different problems. The first begins in the wet product during manufacture and storage. The second begins on the dry surface after exposure to moisture, dirt and outdoor conditions.

BIT, CMIT/MIT, OIT and DCOIT all belong to the isothiazolinone family, but formulators do not use them for the same job. BIT and CMIT/MIT mainly protect water-based products in the wet state. OIT mainly protects cured or curing materials from fungal growth. DCOIT also works in finished materials, with important uses where algae or marine fouling add to the microbial challenge.

BIT and CMIT/MIT Mainly Protect the Product Before Use

Water-based paints, polymer emulsions, pigment slurries, adhesives, cleaners and construction chemicals can support microbial growth during production and storage. Contamination can cause odor, gas, viscosity loss, discoloration or complete product failure before the material reaches the customer.

Foconsci’s CMIT/MIT is an in-can preservative for water-based products. It’s active normally combines chloromethylisothiazolinone and methylisothiazolinone in a 3:1 ratio. It gives broad control of common bacteria, yeasts and molds at low active levels and fits acidic to mildly alkaline water-based systems. This makes it useful in products such as paints, polymer dispersions, adhesives, mineral slurries, detergents and process water.

BIT serves many of the same product groups, but it becomes especially useful when the formulation is neutral to alkaline or faces more heat during production. Foconsci’s BIT preservatives are used in aqueous coatings, polymer dispersions, plasters, synthetic adhesives, pigment slurries, concrete additives and cleaners. BIT also has low volatility and strong thermal and alkaline stability.

CMIT/MIT is often chosen for efficient broad-spectrum control in compatible water-based systems. BIT is often chosen when storage stability, processing temperature or alkaline pH makes the preservation environment more demanding.

OIT Protects the Material After It Dries or Cures

Once paint, sealant or adhesive dries, the preservation target changes. Bacteria inside the liquid product are no longer the main concern. Moisture on the finished surface allows mold and other fungi to grow, causing stains, odor and gradual damage.

Foconsci’s OIT provides fungicidal protection in both water-based and solvent-based materials and remains in the cured or curing composition. Common applications include interior and exterior paints, wood and paper coatings, adhesives, sealants, mastics, caulks, grouts, leather and textiles. THOR

OIT can contribute to wet-state fungal control, but that does not make it a direct replacement for BIT or CMIT/MIT. A water-based coating may still need a dedicated in-can preservative for bacterial contamination and OIT for mold growth on the applied film. The two preservatives protect the same product at different points in its life.

DCOIT Is Used Where Finished Surfaces Face a Stronger Outdoor Challenge

Dichlorooctylisothiazolinone (DCOIT), also belongs on the finished-material side of the comparison. It provides protection against fungi and algae in coatings and other treated materials. Its best-known specialist use is in marine antifouling coatings, where the coating must control biological growth on submerged surfaces. DCOIT is the active ingredient used in antifouling systems such as SEA-NINE 211. The European Union has approved DCOIT as an active substance for antifouling product type 21, subject to the conditions of that authorization. European Commission

Its use is not limited to ship hulls. DCOIT also appears in exterior coating protection, wood-preservation systems, sealants and antimicrobial polymer or PVC applications.

The useful difference between OIT and DCOIT is therefore not simply that one is “stronger.” OIT is a common dry-film fungicide for coatings, adhesives, sealants and related materials. DCOIT becomes more relevant when the finished material needs algal control, marine antifouling performance or protection in a specialized polymer system. The exposure and the organisms present should decide between them.

Choose by the Location of the Microbial Problem

Contact Foconsci Chemical’s sales team to obtain information on our preservative product range.