Particle Testing Case Study: Praxair Surface Technologies

Particle Testing
A particle testing professional at IST analyzing a sample on the Beckman Coulter Multisizer™ 4 Coulter Counter, which measures particle size from 0.4 to 1,600 micrometers.

How Particle Testing Analysis Helps Praxair Surface Technologies Make Stronger, Longer Lasting Protective Coatings For Diverse Products


Leading global supplier of surface-enhancing processes and materials counts on ImmunoSite Technologies particle testing services to ensure the highest quality for coatings that protect and endure in harsh environments

Praxair Surface Technologies, a leader in the development of surface-enhancing processes and materials, produces and applies metallic and ceramic coatings that protect critical metal components from a variety of environmental conditions, including wear, corrosion, and high temperatures. Praxair’s innovative coatings help their customers to reduce maintenance, lower operating costs, increase product life, and improve efficiency and performance. Customers seeking these benefits come from a wide range of industries, including aviation, energy (power generation and oil/gas/petrochemical), and other industrial markets; including automotive, chemical, food and beverage, glass, paper, plastics, printing, steel, and textiles.

Praxair Surface Technologies, with 2010 sales of $568 million and headquarters in Indianapolis, Indiana, is a subsidiary of Praxair Inc., one of the largest industrial gases companies in the world and a Fortune 300 company with 2010 sales of $10.1 billion.


In order to develop higher-performing surface-enhancing coatings, Praxair Surface Technologies requires that critical components of the surface coatings are within very specific particle size distribution (PSD) specifications. They need reliable, knowledgeable particle size analysis services to meet, maintain and document quality assurance for their coating products.


On a regular basis, Praxair sends samples of surface coating materials, such as aluminum and chrome alloy powders, to be analyzed for particle size distribution (PSD) to a team of particle testing experts at ImmunoSite Technologies, Inc. (IST), in Fort Lauderdale, FL. IST’s particle testing laboratory has the expertise and instrumentation to provide the precise particle size analysis needed by Praxair’s engineers and quality assurance professionals.

The Particle Sizing Technology

The process begins with careful preparation of the samples for analysis at IST using a precise, custom preparation procedure. As is often the case with laboratory tests, the right preparation is critical to obtain good results. The IST particle testing professionals then analyze the sample on an instrument called the Multisizer™ 4 Coulter Counter, manufactured by Beckman Coulter, Inc.

This instrument uses TThe Coulter Principle: the reference method for particle sizing.he Coulter Principle (also called the Electrical Sensing Zone Method), which is the accepted “Reference Method” throughout the world for particle size distribution analysis. The Coulter method of sizing and counting microscopic particles is based on measurable, proportional changes in electrical resistance produced by nonconductive particles suspended in an electrolyte solution as they pass through a sensing zone.  As each particle passes through the sensing zone, it displaces its own volume of electrolyte.  The volume displaced is measured as a voltage pulse; the height of each pulse being proportional to the volume of the particle.  The Coulter Principle was developed by Wallace H. Coulter, founder of Coulter Corporation, now Beckman Coulter Inc.

On the instrument, the quantity of suspension drawn through the aperture is precisely controlled to allow the system to count and size particles one by one for an exact reproducible volume in the range of 0.04 to 1,600 micrometers. Several thousand particles per second are individually counted and sized with great accuracy, independent of particle shape, color and density. The result is a report on the number of particles measured, the particle size distribution (volume), and the surface area in one measurement. The instrument uses a Digital Pulse Processor (DPP) that provides ultra-high resolution and multiple channel analysis, for accuracy that is simply not attainable by other technologies.

Particle Characterization:_Volume-Size_Distribution

A typical particle testing report from ImmunoSite Technologies includes graphs such as this sample showing the distribution of particles based on size and volume. This particular sample has particles that are between 2 and 20 micrometers in size, with a mean of 3.054 micrometers and a standard deviation of 1.40 micrometers.

Particle Testing Ensures Quality PerformanceThe Coulter Principle, an Overview

“Our customers count on us to provide a coating that solves wear problems and meets their performance and protection needs,” says Lauren Walkup, Quality Engineer at Praxair, “and in turn, for a number of years now we have relied on IST’s Particle Testing team to ensure that we are meeting critical specifications of the coating’s particle size.  It is through this attention to quality assurance that our customers can rely on Praxair’s advanced surface coating technologies to increase the life and wear of their products, improving their performance and cost-effectiveness.”

“We’re proud to help Praxair provide their customers with superior coating products,” says Carlos Aparicio, COO at ImmunoSite Technologies. “IST has the expertise, instruments and experience to help companies with particle characterization of a wide range of particulate samples, and we’re always ready to consult with clients about the best approach to addressing needs for process or production quality control.”