HTS Coatings — machining & grinding

Aluminum

99.5% Al

  • Arc

Thermal-sprayed aluminum — TSA — is the offshore coating standard, and it has been for forty years. Arc-spray a thin film of 99.5% aluminum wire onto grit-blasted steel and you get something paint cannot match: a sacrificial galvanic anode bonded to the surface. Aluminum corrodes first. Steel stays cathodic. Damage the coating and the surrounding aluminum still polarizes the exposed steel below -800 mV. It is self-healing at every scratch and holiday.

We apply TSA per AWS C2.23 / NACE No. 12 / SSPC-CS 23 and ISO 2063. Typical build is 8 to 20 mils — 200 to 500 microns — on SSPC-SP 10 white-metal blasted steel. As-sprayed porosity runs 15 to 20%, so for splash-zone and submerged service we seal with aluminum-pigmented silicone or two-part epoxy. That sealer is not optional offshore; it is the reason Conoco's Hutton TLP risers, installed 1984 with 200-micron TSA, hit their 20-year design life and kept going past 30.

This is a corrosion coating, not a wear coating. At 30 to 65 HV, aluminum is soft. The value is duty cycle: offshore platforms, LNG tank exteriors, sour-gas piping externals, CUI on insulated stainless to 538°C, bridge steel, marine hardware, splash-zone tie-rods. Twenty to thirty years maintenance-free where paint is a two-to-five-year recoat.

Send us the asset, the service temperature, and the environment. We'll spec the thickness, sealer, and topcoat.

Technical data

Hardness
30-65 HV typical as-sprayed (soft metallic aluminum); ~33-36 HV0.025 at standard arc-spray air flow rates; up to ~210 HV reported for optimized arc-spray coatings at 350-400 um thickness
Bond strength
1,000-3,000 psi typical for arc-sprayed 99.5% Al on grit-blasted steel per AWS C2.23 / ISO 2063; up to ~4,380 psi (30.2 MPa) measured on optimized arc-spray samples; ISO 2063-2 minimum adhesive strength criteria apply
Max service temp
1000°F (538°C) sustained in dry service per AWS C2.23 guidance; ~1100°F (593°C) short-term limit approaching Al melt at 1215°F (657°C)
Max service temp
538°C sustained; 593°C short-term; aluminum melts at 657°C
As-sprayed porosity
5-15% typical arc-sprayed; 15-20% at heavier build thickness; sealing (silicone-aluminum, epoxy, or vinyl wash primer) is CRITICAL for wet or splash-zone service
Typical thickness
8-20 mils (200-500 um); AWS C2.23 / Hutton TLP reference spec 200 um (~8 mils); North Sea practice 250-400 um (10-16 mils) sealed with epoxy and optional PU topcoat
Density
~2.7 g/cc bulk aluminum; deposited coating ~2.3-2.5 g/cc including porosity

Where it earns its keep

  • Proven 20+ year service life in North Sea and Gulf offshore splash zone — Hutton TLP (1984) exceeded 20-year design, field studies document 30+ years maintenance-free with proper sealer
  • Sacrificial galvanic protection works even when coating is damaged — polarizes steel below -800 mV with up to 90% coating loss
  • Industry-standard spec coverage: AWS C2.23 / NACE No. 12 / SSPC-CS 23 / ISO 2063-1 and -2 all cover application, thickness, adhesion, and sealing
  • Applied via arc spray (twin-wire) at high deposition rates — field-practical for large structures like jackets, bridges, and tank farms
  • Handles CUI (corrosion under insulation) to 538°C sustained — effectively the only passive coating system qualified for high-temperature insulated piping externals

Where it doesn't

  • Soft metal — 30-65 HV hardness is orders of magnitude below ceramic or carbide wear coatings; TSA is a corrosion coating, not a wear coating
  • As-sprayed porosity (15-20% on heavy builds) requires sealing for any wet service; unsealed coatings still protect galvanically but degrade faster
  • Surface prep is unforgiving — SSPC-SP 10 / Sa 2.5 white-metal blast and angular profile are non-negotiable per AWS C2.23
  • Application cost is high vs. paint; the 20-30 year life-cycle cost justifies it on critical offshore and CUI assets, not on low-value steel
  • Not suitable for strong acids, strong alkalis, or electrolytes that attack aluminum passive film (e.g., pH < 4 or > 9 without topcoat)

Typical applications

  • Offshore oil and gas platform structural steel (jackets, topsides, columns)
  • Riser pipes, tethers, and TLP (tension-leg platform) components — Hutton TLP reference installation 1984
  • Splash-zone and submerged marine steel (wave-affected hardware, tie-rods, anchor chains)
  • Sour-gas and high-temperature piping externals — CUI (corrosion under insulation) barrier to 1000°F
  • LNG tank exteriors and cryogenic piping — up to 25-30 years maintenance-free CUI service
  • Highway and rail bridge steel — DOT spec for 20+ year service before maintenance
  • Marine hardware, ship decks, flight-deck steel, coastal infrastructure
  • Wind tower bases and foundations in marine and coastal atmospheres

Industries

  • Offshore oil and gas (North Sea, Gulf of Mexico, subsea)
  • LNG import, export, and regasification terminals
  • Marine and shipbuilding (Navy, Coast Guard, commercial)
  • Bridge and civil infrastructure (DOT, highway, rail)
  • Petrochemical and sour-gas piping
  • Power generation (coastal, offshore wind)
  • Water and wastewater steel structures

Substrates

  • Carbon steel (primary substrate per AWS C2.23 / ISO 2063)
  • Low-alloy structural steel (A36, A572, offshore grades)
  • Stainless steel (304, 316 — especially for CUI on austenitic piping)
  • Duplex and super-duplex stainless piping

Sources

Data points on this page draw on the following published references. Nothing here replaces a material-specific review by our process engineers — but it's the working starting point.

Material data on this page is provided as a general reference and can vary by lot, substrate, and application. Contact HTS to confirm the right material and specification for your specific part.

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