Why Your Paint Tanks Still Settle Pigments? (90% Factories Use Wrong Mixic Logic)

Introduction

Most paint and coating manufacturers face the same troublesome issue: pigment settling occurs even with agitators running continuously.

Many factories try to solve the problem by increasing rotation speed, adding more anti-settling agents, or cleaning tanks more frequently. However, these methods only increase production costs and cannot fundamentally eliminate sedimentation.

After years of testing and site debugging, we found that most pigment settling problems are not caused by raw materials, but by wrong mixing logic and improper agitator selection.

This article will break down the three most common industry mistakes and explain the correct anti-settling mixing principle for paint storage tanks.

Three Common Misunderstandings That Cause Pigment Sedimentation

Mistake 1: High-shear mixing equals anti-settling

Many factory owners confuse “dispersion” with “suspension”. High-shear turbine impellers are designed for breaking agglomerates during production. However, in storage tanks, excessive shear will not improve suspension. Instead, it may cause paint delamination, bubble generation and viscosity instability.

Mistake 2: Faster speed means better mixing effect

Blindly increasing speed will only create violent surface swirling, while the bottom fluid remains static. The high speed consumes more power but fails to form effective up-and-down circulation. Heavy pigments continue to accumulate at the tank bottom.

Mistake 3: Using reaction tank agitators for storage tanks

Reaction tanks and storage tanks have completely different mixing purposes. Reaction focuses on homogenization and reaction acceleration, while storage focuses on long-term stable suspension. Direct reuse of reaction mixing equipment will inevitably produce dead zones and sediment accumulation.

Real Root Cause of Tank Sedimentation

Stable pigment suspension relies on overall vertical circulation, not local turbulence.

If the agitator cannot form an effective up-and-down flow field, the bottom liquid will stay static. Heavy inorganic pigments such as titanium dioxide, iron oxide and fillers will settle rapidly under gravity.

The key factors leading to settlement failure include:

• Radial flow impeller used instead of axial flow impeller

• Insufficient bottom sweeping flow

• Unreasonable installation height and angle

• Lack of baffle design, resulting in invalid vortex rotation

Correct Mixing Logic for Paint Storage Tanks

For paint and coating storage tanks, low shear + large flow + vertical circulation is the standard anti-settling principle.

Axial flow hydrofoil impellers and pitched blade impellers are the most suitable options. They push the liquid from the top down to the tank bottom, then lift the settled pigments upward again, achieving full tank suspension without damaging the paint system.

Agitator Selection by Different Tank Working Conditions

1. Small and medium-sized tanks (below 10m³)

Top-entry agitator with axial flow impeller is the most cost-effective solution, realizing full uniform circulation.

2. Large storage tanks (above 10m³)

Large-diameter tanks easily produce bottom dead zones. Side-entry agitators are highly recommended. The oblique impact flow completely sweeps the tank bottom, thoroughly solving pigment accumulation, with lower energy consumption than top-entry high-power equipment.

3. Explosion-proof solvent-based paint workshop

Equipped with full explosion-proof motor and sealed drive system to meet coating industry safety standards.

Actual Improvement Effect After Optimization

After replacing the correct agitator configuration, most of our customers achieve the following improvements:

• Zero obvious pigment sediment during long-term storage

• Consistent color batch stability

• Reduce tank cleaning frequency by 70%

• Save labor cost and production downtime loss

• Avoid waste of paint materials caused by delamination

Conclusion

Pigment settling is not an inevitable problem in the coating industry. Most sedimentation failures come from mismatched mixing schemes and incorrect industry experience.

Only by adopting low-shear circulating suspension technology according to actual tank volume and paint characteristics can manufacturers completely solve the long-term settling problem.

If your paint storage tanks are still troubled by pigment deposition, color difference and frequent tank cleaning, welcome to contact us for professional mixing scheme optimization.