Thermal%20Spray%20Coatings%20of%20Zinc%20and%20Aluminum%20Zinc%20Metallizing

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Thermal Spray Coatings of Zinc and AluminumZinc
Metallizing
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• Prepared byJim Weber - Sulzer Metco (US) Inc.
  Westbury, NY
• Thermal Spray Materials Development
• Systems Engineering
• Equipment Research Development
• Field Service Manager
• Training Manager
• Quality Assurance Manager
• Currently the Product Line Manager for industrial
  markets, focusing on combustion (wires, powder,
  HVOF) and arc equipment
• Latest industry focus - working with NACE
  International (National Association of Corrosion
  Engineers) and the petrochemical industry to
  solve Corrosion Under Insulation (CUI) problems
  with Thermal Spray Aluminum (TSA) coatings and
  with the Gas Technology Institute (GTI) solving
  natural gas transmission and metering station
  corrosion problems.

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Information

• A brief introduction to thermal sprayed coatings
  are of Zn (TSZ), Al (TSA), and their alloys
  (85/15 Zn/Al), and how they provide long term
  corrosion protection
• Some examples of where are these coatings are
  used and how they have performed
• A brief introduction to galvanizing and its
  comparison to thermal spray coatings
• An overview of the most popular types of
  equipment that apply these coatings
• Question answer session

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What is Thermal Spray?

• Thermal spray is NOT a welding process
• Thermal spray coatings are a melted, or softened
  ceramic, metallic, or polymer materials are
  transported by a gas stream to a properly
  prepared substrate

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What is Thermal Spray?

• These coatings are typically mechanically bonded
  to a grit blasted surface
• Metals that feed into the thermal spray gun are
  the actual coatings. There are no solvents or
  VOC's.
• The coatings are similar to the metals being
  sprayed, however there are some important
  differences
• There are metal oxide stringers and porosity in
  the coatings
• Metal particles in the coating create a layered
  effect within the coating structure
• Due to the rapid cooling of the metal particles
  as they adhere to the substrates, thermal sprayed
  coatings have unique crystalline structures not
  normally found in wrought metals
• Almost any material can be thermal sprayed onto
  almost any substrate

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What is Thermal Spray?

• Thermal spray, especially with soft metals
  sprayed with the combustion wire equipment, is a
  relatively cold process. Substrate temperatures
  seldom reach gt200F/95C.

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How thermally sprayed coatings of Zn and Al,
combat corrosion

• For atmospheric, buried, and marine environment
  corrosion protection, Zn (TSZ), Al (TSA), and
  their alloys have proven that they provide long
  term corrosion protection and outperform most all
  other methods.
• Anodic (TSZ/TSA) metal coatings applied to steel
  cathodes (more noble than Zn or Al), are referred
  to as cathodic or sacrificial protection coating
  systems.
• These thermal spray coatings provide corrosion
  protection by excluding the environment (or
  electrolyte) and acting as a barrier coating
  (like paints, polymers, and epoxies), but unlike
  typical barrier coatings they also provide
  sacrificial anodic protection.

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Typical thermal spray applications or Zn, Al,
and their alloys

• Hundreds of bridges have been thermal sprayed
  (metallized) over the past 100 years. There are
  many document cases of gt50 years of corrosion
  protection provided by thermal spray coatings.
• Zinc and zinc alloys are also sprayed directly
  onto concrete to protect the steel rebar within.

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Typical thermal spray applications for Zn, Al,
and their alloys
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Typical thermal spray applications for Zn, Al,
and their alloys

• Carbon steel equipment (petrochemical facilities,
  power generation, Naval ships, etc.) are coated
  with TSA, TSZ, and 85/15.
• Petrochemical users expect TSA coatings to
  provide gt20 years with no maintenance or
  corrosion inspections.
• A TSA coating has been operating in severe
  petrochemical vessel operating conditions. One
  coating in particular has protecting carbon steel
  equipment operating in cyclic service of ambient
  to 350F/175C, in contact with wet insulation, for
  gt50 years with no visible corrosion .
• TSA coatings are also specified as a solution to
  stress corrosion cracking (SCC) of austenitic
  stainless steel.
• Offshore oil rigs operating in severe conditions
  rely on thermal spray aluminum for corrosion
  protection. gt20 service life with no maintenance
  has been documented.
• These coating systems meet specifications from
  organizations such as NACE, SSPC, AWS, US Navy,
  US Army Corps of Engineers, and many others.

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Petrochemical applications
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Petrochemical applications
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Petrochemical applications
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Navy corrosion applications

• The Navy has many documented uses for thermal
  spray coatings of all types, including corrosion
  coatings
• High temperature (gt900F/480C) steam valves and
  associated piping have been protected by thermal
  sprayed aluminum on Naval ships. It is documented
  that these coatings lasted longer than 5 years in
  areas where paint coatings had lasted only months.

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Hot-Dip Galvanizing

• Hot-dip galvanizing is essentially a brazing
  process. Steel is cleaned (mechanically and
  chemically) and then heated to gt850F in a molten
  zinc bath. The molten zinc reacts with the
  surface of the steel and forms a coating of
  various layers of zinc and iron alloys,
  depositing a layer of material that is
  approximately 40 pure zinc.
• A. Degreasing in a hot, alkaline solution
• B. Rinsing thoroughly in a water rinse
• C. Pickling in a hot, acid bath
• D. Rinsing thoroughly in a water rinse
• E. Prefluxing in a zinc ammonium chloride
  solution
• F. Immersing the article in the molten zinc
  through a molten flux cover (usually zinc
  ammonium chloride)
• G. Finishing (dusting with ammonium chloride to
  produce a smooth finish).
• H. Sometimes step F is followed by immersion of
  the zinc coated article in a quench bath which
  may contain a dichromate solution.

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Hot-Dip Galvanizing
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Hot-Dip Galvanizing
Galvanized Coating
Thermal Spray Coating
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Galvanizing VS. Thermal Spray

• Pure aluminum (gt99), zinc (gt99.9), and
  zinc-aluminum alloys may be sprayed, whereas
  galvanizing is never pure zinc, it is Zn/Fe
  matrix. Also, the molten zinc bath is often
  contaminated with pickup from materials that are
  dipped into it.
• Aluminum and the 85/15 zinc-aluminum alloy
  coatings are not available by hot dip
  galvanizing.
• Aluminum and Zn/Al coatings protect steel better
  than pure zinc in marine and industrial
  environments.
• When metalizing, the surface being coated is not
  preheated and it remains at a low temperature,
  with local temperature never exceeding about
  250-300 F. Because metalizing is a "cold
  process" when compared to galvanizings gt850F
  temperature, there is virtually no risk of weld
  damage or distortion of the steel due to high
  temperatures or overheating

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Galvanizing VS. Thermal Spray

• The acids, fumes, contaminated rinse water, and
  other byproducts of the galvanizing process are
  considered hazardous. Thermal spray waste is
  generally metal dust, which when applied in a
  shop environment, is collected by specially
  designed dust collectors that remove up to 99.99
  of the generated dust, down to .12 microns, and
  may be recycled. Metal dust generated while
  spraying onsite may be ignored, swept up, or
  collected with grit blasting containment and
  collection systems depending on local
  requirements and conditions.
• Due to environmental concerns, new galvanizing
  lines are no longer permitted in many states,
  including NY state. The lines that are currently
  running must be updated to current environmental
  regulations within a set time frame, as dictated
  by local, state, and federal codes for hazardous
  waste and emissions.
• Most paint and powder coating applicators can
  easily upgrade to thermal spray coatings. It is
  difficult, or impossible to upgrade to a
  galvanizing line, therefore fabricated parts must
  be shipped to approved galvanizers and then
  shipped back to approved painters/powder coaters.
  

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Galvanizing VS. Thermal Spray

• Because galvanized coatings must be dipped in a
  tank, parts are limited to the size of the molten
  zinc galvanizing tank.
• While galvanized coatings are difficult to top
  coat and may require special surface preparations
  (acid etching, phosphating, etc.) to allow
  topcoats to adhere to them, thermal spray
  coatings 5-15 porosity make them a perfect
  surface for paints and powder coats. The coating
  soaks up topcoats like a sponge, creating a
  tremendous bond between the metal coating and the
  top coat.
• Thermal spray coatings are also less susceptible
  to out-gassing, a phenomenon that causes bubbling
  and loss of adhesion of topcoats.
• Field repairs to galvanizing can only be done
  with paint, which does not last nearly as long as
  the galvanized coating. Typical thermal spray
  equipment is portable and easily used onsite in
  the field. An added benefit to this equipment is
  its low cost, less than 12,000 for a complete
  portable system.

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Galvanizing VS. Thermal Spray

• The Use of Thermal Sprayed Zinc Alternative to
  Hot Dipped Galvanizing Joseph G. Radzik,
  Director of Engineering Research Development,
  Tyco Fire Building Products
• Representative samples of Thermal Sprayed Zinc
  and Hot Dipped Galvanized ductile iron castings
  conforming to ASTM2 A 536, Grade 65-45-12, were
  subjected to a 5 salt spray fog test at 95 F in
  accordance with ASTM B 117. Coating thickness was
  measured in the range of 3.4 to 5.5 mils for all
  samples evaluated, which conforms to the industry
  requirement for grooved piping products. An
  independent laboratory NADCAP accredited in
  materials and nondestructive testing methods
  performed the testing. After 120 hours exposure,
  the Hot Dipped Galvanized samples exhibited red
  corrosion. The Thermal Sprayed Zinc samples did
  not exhibit red rust corrosion. Testing was
  continued on the Thermal Sprayed Zinc samples for
  an additional 72 hours for a total of 192 hours
  and examined for signs of red rust. None of the
  Thermal Sprayed Zinc samples exhibited this
  condition and testing was stopped.

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• Ski-Lift Maintenance Wire Arc Spray
  vs.Galvanizing, M. Bhursari and R. Mitchener,
  SSPC International Conference, 1998.
• This paper reviews the use of wire arc spray zinc
  vs. galvanizing on ski lifts. The authors discuss
  a case study in which painted lifts required
  repainting every 3 years, hot dipped lifts showed
  signs of corrosion in fewer than 5 years and
  thermal sprayed ski lifts exhibited no corrosion
  after 5 years. It was estimated that the wire
  arc-spray zinc coating, depending upon the
  thickness, would have a life expectancy of 20
  years with minimal maintenance. The authors
  concluded that thermal spray coatings were more
  resistant to abrasion and wear than thin
  galvanized coatings.

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Combustion Wire System
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Combustion Wire System
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Combustion Wire System
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Combustion Wire System
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Combustion Wire System
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Combustion Wire System
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Combustion Wire System
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Twin Wire Arc System
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Twin Wire Arc System
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Twin Wire Arc System
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Twin Wire Arc System
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Twin Wire Arc System
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Twin Wire Arc System
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Twin Wire Arc System
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Twin Wire Arc System