Skip to content

Arc Resistance - Concepts and Testing Explained

Insulating materials such as Teflon, plastic, rubber, ceramic, or glass ensure products function properly and safely. However, no insulator is perfect. These materials still contain trace amounts of mobile charges that can carry current. Non-conductive polymeric coatings provide critical protection to electronic components, but these materials can become conductive when electric current travels along their surfaces due to chemical and thermal decomposition and material erosion. Therefore, the arc resistance electric property is considered when selecting materials where reliable insulation is a priority.

 

Arc Resistance Definition

Arc resistance is defined as the ability of an insulating material to withstand a high voltage, low current arc and resist the development of a conducting pathway along its surface. More specifically, it measures the time in seconds an electrical arc may exist on an insulator’s surface before the material’s breakdown occurs.  

Arc resistance coating on a PCB

Significance

This property is helpful as a design criterion to choose materials for situations vulnerable to electric arcing but serves other purposes, acting as:

  • A quality control method
  • A way to screen materials for applications susceptible to arcing
  • Determining changes in insulation behavior due to aging, irradiation, exposure to temperature or humidity, chemical and thermal decomposition, contamination, and erosion

Arc Resistance Testing

The ASTM D495 test uses a high-voltage, low-current arc to simulate service conditions and evaluate dry, uncontaminated samples. According to the ASTM D945 arc resistance test, specimens are placed between electrodes, and an arc is generated at specified current densities and scheduled intervals. The total elapsed operation time until test failure determines a material’s arc resistance.

Several arc testers that comply with this test method are commercially available.

Test Methods ASTM D 2132, D 2303, and D 3638 entail wet testing with contaminated specimens.

How to Improve Arc Resistance

Differing molecular structures, formulation ingredients such as curing agents, and physical and chemical surface conditions cause arc resistances of coatings to vary widely. Fillers, such as glass or mineral fillers, can improve the arc resistance of polymer coatings, easily doubling or tripling the arc resistance of unfilled epoxy resin systems.  

Additionally, resistance increases when the coating surface is kept dry and contaminant-free. Even touching the surface will reduce resistance due to moisture, oils, and salts transferred from the fingers.

 

Choosing The Right Coating

Not all coatings have exact arc resistance values due to issues with testing. Some crack, gum up, or melt during testing. When precise values that can be reproduced are acquired, they result from the material’s stability, purity, and surface cleanliness. If you need to evaluate material for a project, you can ask coating suppliers if an exact value is available.

Contact us or read about other critical electric thin film properties, such as volume resistivity or dissipation factor

 

Additional Resources

The Difference Between
Video

The Difference Between "Hydrophilic and Hydrophobic" Coating Properties

Ensure Your Products Meet Market Claims With Our IP Ratings Checklist
Checklist

Ensure Your Products Meet Market Claims With Our IP Ratings Checklist

Learn About Corrosion Resistance From An Industry-Leading Engineer
Webinar

Learn About Corrosion Resistance From An Industry-Leading Engineer

Understand the Capabilities of Thin Film Coatings With Our Resource Page
Resource

Understand the Capabilities of Thin Film Coatings With Our Resource Page

Understand UL94 Rating - Testing, How to Choose a Material, and More
Blog

Understand UL94 Rating - Testing, How to Choose a Material, and More

Learn About HZO Parylene With Our Resource Page
Resource

Learn About HZO Parylene With Our Resource Page

What's the Difference Between Hydrophobic Coatings and Hydrophilic Coatings?
Blog

What's the Difference Between Hydrophobic Coatings and Hydrophilic Coatings?

Download HZO's Nanocoating Datasheet
Datasheet

Download HZO's Nanocoating Datasheet

Learn About the Costs of Corrosion
Infographic

Learn About the Costs of Corrosion

Understand How to Avoid Premature Product Failure
Webinar

Understand How to Avoid Premature Product Failure

Learn About Waterproof and Corrosion Resistant Coatings
Webinar

Learn About Waterproof and Corrosion Resistant Coatings

Why You Need HZO Protection For Your Electronics
Video

Why You Need HZO Protection For Your Electronics

HZO Coating Demo Video
Video

HZO Coating Demo Video

How To Design a Waterproof Product With IP Ratings
Blog

How To Design a Waterproof Product With IP Ratings

How To Prevent Devices From Overheating
Blog

How To Prevent Devices From Overheating

NEMA Enclosure Ratings vs IP Standards
Blog

NEMA Enclosure Ratings vs IP Standards

Arc Resistance - Concepts And Testing Explained
Blog

Arc Resistance - Concepts And Testing Explained

Dielectric Strength - Formula, Testing, Table of Values
Blog

Dielectric Strength - Formula, Testing, Table of Values

Dielectric Constant of Insulator - Materials, Formula, Table of Values
Blog

Dielectric Constant of Insulator - Materials, Formula, Table of Values

Military Standards for Safeguarding PCBAs
Blog

Military Standards for Safeguarding PCBAs

Tensile Strength at Yield - Testing, Definition, Material Selection
Blog

Tensile Strength at Yield - Testing, Definition, Material Selection

Elongation At Break - Definition, Testing, Material Selection
Blog

Elongation At Break - Definition, Testing, Material Selection

Elongation Yield Overview - Unit of Measurement, Data, Testing
Blog

Elongation Yield Overview - Unit of Measurement, Data, Testing

Young's Modulus of Polymers - Measurement, Calculation, Material Selection
Blog

Young's Modulus of Polymers - Measurement, Calculation, Material Selection

Dissipation Factor - Definition, Measurement, Variables
Blog

Dissipation Factor - Definition, Measurement, Variables

Volume Resistivity - Definition, Measurement, Implications For Product Design
Blog

Volume Resistivity - Definition, Measurement, Implications For Product Design

Biocompatible Coating Material
Blog

Biocompatible Coating Material

Transparent Polymers - Applications, Material Selection
Blog

Transparent Polymers - Applications, Material Selection

WVTR - Coating Standards, Testing, Material Selection
Blog

WVTR - Coating Standards, Testing, Material Selection

What is the Index of Refraction? Measurement, Definition & More
Blog

What is the Index of Refraction? Measurement, Definition & More

What is Thermal Conductivity? Explanation, Measurement, Uses
Blog

What is Thermal Conductivity? Explanation, Measurement, Uses

Polymer Glass Transition Temperature – Material Properties, Impact
Blog

Polymer Glass Transition Temperature – Material Properties, Impact

What is Coefficient of Linear Expansion? Formula, Units & More
Blog

What is Coefficient of Linear Expansion? Formula, Units & More

Prevent Electronic Failure Webinar
Webinar

Prevent Electronic Failure Webinar

Safeguarding with Nanocoatings Webinar
Webinar

Safeguarding with Nanocoatings Webinar