Thermal Spray Coating Application Presented by Dean Hooks

Thermal Spray Coating Application Presented by: Dean Hooks, Thermion

Scope • This webinar defines thermal spray coating (TSC) and provides an overview of its application and uses

Introduction • This webinar will review the procedures for the application of metallic thermal spray coatings (TSCs) of aluminum, zinc, and their alloys and composites for the corrosion protection of steel • Required equipment, application procedures, and in-process quality control (QC) checkpoints will be discussed

What is Thermal Spray?

Thermal Spray Coating (TSC) Materials • Aluminum, zinc, and their alloys in the form of powder or wire heated to a plastic or molten state

How do TSCs Protect Steel? • Sealed: Good barrier protection • Unsealed: Galvanic (sacrificial) protection

Special Properties • Very good resistance to high temperatures, sunlight, and weathering • Good application properties: adhesion to metals, film build, edge retention, and transfer efficiency • Good impact and abrasion resistance • Attacked by acids or alkalis unless topcoated

Environmental Advantages • No volatile organic compounds (VOCs) to cause air pollution (100% solids) • No hazardous air pollutants (HAPs) • Limited overspray into surrounding areas

Economic Advantages • Long-term protection (40+ years) of steel structures resulting in low life-cycle costs (costs per year) • Reduced rework for original coating defects • Reduced maintenance over coating life

SSPC-CS 23. 00/AWS C 2. 23/NACE No. 12 • A procedure for the application of metallic thermal spray coating (TSCs) of aluminum, zinc, and their alloys and composites for the corrosion protection of steel • Required equipment, application procedures, and in-process quality control (QC) checkpoints are specified

SSPC-CS 23. 00/AWS C 2. 23/NACE No. 12 • Currently being revised • Publication date expected in June 2016

SSPC-QP 6 • Qualifies contractors who apply thermal spray coatings

Safety Issues • The basic precautions for thermal spraying are essentially the same as for welding and cutting • Information on safety can be found in: – ANSI Z 49. 1, Safety in Welding, Cutting, and Allied Processes – NFPA 58, Standard for the Storage and Handling of Liquefied Petroleum Gases

Safety Issues • Potential thermal spraying hazards include: – Exposure to vapors, dust, fumes, gases, noise (from the spray gun), and arc ultraviolet (UV) radiation

Single Wire - Flame Spray

Thermal Flame Spray Coatings • Flame spray – Single wire fed into spray gun – Acetylene/oxygen flame melts wire – Compressed air blows melted metal onto surface

Typical TSC Wire Flame-Spray Components • Spray Head (also referred to as a spray gun or pistol) • Fuel Gas, Oxygen, and Air • Wire and Feed Unit • System Controls (gas and wire)

Typical TSC Wire Flame-Spray Components

TSC Wire Caddy and Control

Wire Flame-Spray Head

TSC 3/16 -inch Zinc Wire

Thermal Spray Coating System Requirements

Thermal Spray Application Process • Coating thickness should be attained in several overlapping passes • Acceptability should be confirmed by tensile adhesion testing – Bend Test – Cut Test

TSC Wire Flame-Spray

Twin Wire Arc Spray

Typical Arc Spray Installation

Electric Arc Thermal Spraying in Progress

Arc Spray Application

Thermal Spraying onto Blast Cleaned Steel

Thermal Spraying onto Blast Cleaned Steel

Bend Test • 180 degree bend on a Mandrel • Qualitative, testing proper surface preparation, equipment setup, and spray parameters • Mandrel diameter for threshold of cracking depends on substrate and coating thickness

Bend Test • Passes – On the bend radius, there is no cracking or spalling, or only minor cracking that cannot be lifted from the substrate with a knife blade • Fails – Coating cracks with lifting from the substrate

Bend Test

Cut Test • A procedure to identify areas of metallized coating that are poorly adhering • Involves impacting the coating with blow from a hammer to a masonry chisel • Any disbonding or peel of the coating is considered a failure

Cut Test

Cut Test- Pass

Cut Test- Fail

Thermal Spray Repair • Defined as less than 1 square foot area • Mark nonconforming area • Repair the nonconforming area – Feather the damaged area to achieve an 2 -3 inch overlap – Apply the TSC to the newly prepared surface, and overlap the existing TSC to the extent of the feathered edge so the overlap is a consistent thickness

TSC on Highway Structure Holding Signs

TSC on Piling in Immersion Service

TSC Applied to Girders for Atmospheric Service

Thermal-Spray Coated Components of Industrial Structure

Questions?