Coating Additives Explained: Function, Compatibility and Dosage

Binders form the coating film and pigments provide colour or functional properties, but additives help the formulation process, apply and perform as intended. Their effect depends on resin chemistry, pigment type, water or solvent balance, manufacturing sequence and end use. An additive that helps one formulation can cause defects in another.

Wetting agents and dispersants

Wetting agents help liquid contact solid surfaces, while dispersants help stabilize pigment particles after wetting. Selection depends on pigment surface chemistry, binder, pH and the rest of the formulation. Poor compatibility can lead to flocculation, colour-strength changes, viscosity drift or storage instability.

Defoamers and air release

Foam can arise during mixing, pumping or application. Defoamers help destabilize bubbles, but excessive or incompatible defoamer may cause craters, poor intercoat adhesion or surface defects. Test the lowest effective dosage over the full process, not only in a small cup.

Rheology modifiers

Rheology modifiers influence flow, sag resistance, settling and application feel. Their performance can depend on shear history, pH, electrolyte content and other additives. Check viscosity at relevant conditions and assess both in-can stability and applied-film appearance.

Other additive functions

Substrate wetting aids, coalescents, slip and flow additives, matting agents, preservatives and corrosion inhibitors serve different purposes. Not every coating needs every category. Selection should be driven by a defined performance requirement and confirmed with supplier guidance and controlled trials.

How to establish dosage

Use the supplier’s recommended starting range as a trial guide, not a universal rule. Confirm whether dosage is calculated on total formulation, binder solids, pigment or another basis. Make a controlled ladder of additions, keep other variables fixed, and compare processing, stability and final-film properties.

Store and handle additives correctly

Follow the current safety data sheet and technical data sheet for temperature, shelf life, container closure and handling. Label opened containers and track expiry or retest dates. Avoid stockpiling slow-moving material beyond realistic demand, especially where storage stability is limited.

The takeaway

Additives are formulation tools, not shortcuts. Define the problem, select compatible chemistry, test dosage systematically and evaluate the finished coating under realistic conditions.

Related reading: Paint additive inventory planning | Troubleshoot common paint defects

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