Why Surface Finish Grades are a Key Part of Your Production Vessel

Summary:

• Surface finish grade affects more than appearance, it impacts product safety, yield, and cleanability.
  
• Different industries require different Ra standards, particularly for food, pharma, and cosmetics.
  
• The right finish boosts performance, minimizes contamination risk, and improves operator efficiency.

Surface Finish: More Than Just Looks

The surface finish grade of a production vessel is a critical yet often overlooked factor in mixing and processing success. While it may seem cosmetic, the finish directly impacts the functionality, safety, and sanitation of your vessel.

A vessel’s surface finish will determine what products can be produced within that vessel. From pharmaceuticals to chemicals to food products, each industry has surface finish standards that must be met. And even beyond industry requirements, a vessel’s surface grade can have a big effect on how your product is produced.

How Surface Grades Are Measured

At Lee Industries, surface finish is measured using a profilometer, a device equipped with a fine needle that drags across the surface to detect microscopic peaks and valleys. The tool produces a value known as “roughness average” (Ra), measured in micro inches.

Examples of Ra measurements are:

• Smooth shiny surface/Mirror finish: 6–12 Ra
• Stainless steel/Standard brushed finish: 20–30 Ra
• Mill finish: 100+ Ra

These readings help define whether a vessel is appropriate for sanitary or industrial use.

Sanitary vs. Unsanitary Surface Grades

The biggest distinction among surface grades is whether the finish is sanitary.

• Sanitary finish (typically 20–30 Ra) is critical for eliminating areas where bacteria or contaminants could accumulate.
• Surfaces with exposed welds or rough textures can increase the risk of product contamination, especially in food or pharmaceutical applications.
  

Not All Surfaces Are Created Equal

It’s common for a vessel to feature multiple finishes:

• Interior surfaces and agitators, the areas in direct contact with product, are typically finished to the highest sanitary standard.
• Exterior surfaces may be finished to a lower standard depending on application needs.
  

What to know about common surface finishes

The exact terminology may vary slightly depending on the manufacturer, but in general, most finish grades will fall into one of the following:

How Electropolishing Enhances Surface Performance

Electropolishing is a finishing technique that uses an electric charge to:

• Enhance non-stick properties
• Reduce friction on contact surfaces
  
• Improve corrosion resistance

This upgrade is particularly beneficial in high-viscosity mixing applications, where sticky products like ointments or creams can hinder performance.

Key Takeaways:

• The right surface finish ensures your vessel is ready for the demands of your industry.
  
• Accurate Ra measurement supports compliance, safety, and cleaning efficiency.
  
• Choosing enhanced finishes, like mirror polish or electropolishing, can deliver a better product yield and reduce downtime.

Last Updated: 10/17/2025