What Is Wire Arc Spray Coating? The Process and Where It Fits

What Is Wire Arc Spray Coating?

Wire arc spray coating is a thermal spray process that feeds two consumable metal wires together at an angle, strikes a continuous electric arc between their tips to melt them, and uses a jet of compressed air to atomize the molten metal and propel it onto a prepared surface at roughly 100–150 m/s. Like every thermal spray process, the coating builds up as flattened, rapidly solidified droplets — but arc spray is the only common process that uses electrical energy rather than a combustion flame or plasma plume as its heat source, which makes it simpler, cheaper to run, and easier to take out of the shop and onto a job site.

That combination — no gas cylinders, portable power supply, and wire feedstock that's cheap and widely available — is why wire arc spray (also called twin-wire arc spray, or often just "arc spray metalizing" when applied with zinc or aluminium) is the workhorse process for corrosion protection on large steel structures, and a common choice for dimensional build-up on components too big or too low-value to justify HVOF. For where it sits against the rest of the process family, see our guide on what thermal spray coating is, and for the full process line-up we operate see our technologies page.

How the Wire Arc Spray Process Works

Two wires of the same or dissimilar metal feed continuously through an arc spray gun and converge at a point just past the nozzle tip. A DC power supply (typically 25–40 V) maintains a continuous arc between the two wire tips, melting the metal as fast as it's fed in. A jet of compressed air, aimed directly at the arc zone, atomizes the molten metal into fine droplets and accelerates them onto the substrate.

The arc itself burns locally at several thousand degrees Celsius, but because contact time is short and the compressed-air stream carries most of that heat away from the substrate rather than into it, arc spray puts comparatively little heat into the part — useful when coating thin sections or heat-sensitive substrates. The real limitation is feedstock: both legs of the process must be electrically conductive wire, so arc spray is restricted to metals and metal alloys that can be drawn into wire form. Ceramics and cemented carbides — the materials HVOF, D-Gun, and plasma spray handle as powder — are off the table for arc spray.

Wire Arc Spray vs Flame Spray vs HVOF

Heat source and particle velocity set the ceiling on bond strength and density for every thermal spray process, so the fair comparison is side by side on the numbers a specification actually turns on.

| Property | Wire Arc Spray | Flame Spray | HVOF | |---|---|---|---| | Heat source | Electric arc between two wires | Oxy-fuel combustion flame | Supersonic fuel/O₂ combustion | | Feedstock | Wire only (conductive metals) | Wire or powder | Powder | | Particle velocity | ~100–150 m/s | 80–150 m/s | 600–900 m/s | | Typical bond strength | 15–25 MPa (Zn/Al) | 10–30 MPa | 60–80 MPa | | Typical porosity | 10–20% | 10–15% | < 2% | | Gas infrastructure needed | Compressed air + electricity only | Oxygen + fuel gas cylinders | Oxygen + fuel gas, higher pressure | | Relative cost | Lowest | Low | Moderate | | Best fit | Large-area corrosion protection, build-up | Build-up, repair, non-critical wear | General-purpose hard-chrome replacement |

Arc spray and flame spray occupy similar territory on bond strength and porosity, but arc spray usually wins on running cost and portability since it needs no gas cylinders — just a wire feeder, a power supply, and shop air. Neither comes close to HVOF or D-Gun on density or bond strength, which is why neither is specified for a load-bearing wear surface. See HVOF vs hard chrome for where the high-performance end of the family fits.

Materials Sprayed by Wire Arc

Arc spray's wire-only feedstock still covers the materials that matter most for its core jobs — corrosion protection and structural build-up:

• Zinc wire (TSZ) — sacrificial, cathodic protection for steel in marine and highly corrosive atmospheres; the zinc corrodes preferentially so the base steel doesn't
• Aluminium wire (TSA) — barrier-style corrosion protection with better performance in higher-temperature or industrial-atmosphere service than zinc alone
• Zinc-aluminium pseudo-alloy wire (commonly ~85/15 Zn-Al) — sprayed from two separate wires to combine zinc's sacrificial action with aluminium's barrier durability in one coating
• Mild and stainless steel wire — dimensional build-up and repair on large shafts, housings, and worn machine elements before finish machining
• Bronze and other copper-alloy wire — bearing surfaces and low-friction applications where wear duty is moderate

Where Wire Arc Spray Fits

Arc spray earns its place on jobs where cost, portability, and coverage area matter more than maximum bond strength or minimum porosity:

• Corrosion protection on structural steel — bridges, storage tanks, offshore and onshore platforms, transmission towers — almost always with zinc, aluminium, or a Zn-Al pseudo-alloy, and almost always finished with a sealer or paint topcoat (a "duplex" system) to close the coating's natural porosity
• Large-area work where the part can't be moved into a shop — arc spray guns run off a compressor and a power supply, so they can be taken to the structure
• Dimensional build-up on large, low-duty components — couplings, big shaft journals, housing bores — where HVOF's smaller practical work envelope or higher cost isn't justified
• Bond coats for subsequent overspray or as an economical first pass before a more specialized top coat

Common Mistakes When Specifying Arc Spray

Getting arc spray wrong is usually a matter of specifying it outside its real strengths:

• Specifying arc spray for a sliding wear surface, seal face, or plunger — 15–25 MPa bond strength and 10–20% porosity won't hold up where HVOF or D-Gun tungsten carbide is the correct call; see hard chrome replacement
• Leaving a porous zinc or aluminium coating unsealed in immersion or splash-zone service — the interconnected porosity that's harmless in a mild atmosphere becomes a direct path for corrosive fluid to reach the substrate
• Treating zinc and aluminium as interchangeable — zinc offers stronger sacrificial (cathodic) protection in high-chloride marine environments but is consumed faster; aluminium holds up better at elevated temperature and in industrial atmospheres
• Assuming "metalizing" always means arc spray — flame spray and plasma spray can also deposit zinc or aluminium; arc spray is simply the most common and most economical route for large-area work
• Skipping surface preparation — arc spray's bond is almost entirely mechanical, so an inadequate grit-blast profile is one of the most common causes of premature coating failure

Choosing Between Arc Spray, Flame Spray, and HVOF

A short checklist covers most process-selection decisions:

• Is the goal large-area corrosion protection on structural steel? → Arc spray with zinc, aluminium, or a Zn-Al pseudo-alloy, sealed, is the standard route
• Is the surface load-bearing, sealing, or under sustained sliding wear? → HVOF or D-Gun, not arc spray or flame spray
• Does the coating need to be a ceramic or cemented carbide? → Arc spray can't — it's wire-only; use HVOF, D-Gun, or plasma spray
• Is the part too large to move, or does the job need to happen on site? → Arc spray's portability (no gas cylinders, just air and power) usually wins over flame spray or HVOF
• Is this dimensional build-up on a large, low-duty component before machining? → Arc spray or flame spray, whichever is more economical for the job at hand

Get a Quote for Wire Arc Spray Coating

Lotus Surface Tech is an ISO 9001:2015-certified thermal spray facility in Chennai, Tamil Nadu, established in 2015, operating wire arc spray alongside HVOF, Super-D-Gun, plasma spray, and flame spray, with capacity for components up to Ø800 mm × 7 m. We apply arc spray for structural corrosion protection and dimensional build-up, and will tell you directly when your part actually needs HVOF or D-Gun instead.

Full process capability is on our technologies page. When you are ready to move forward, contact us to get a quote — share your part drawing or structure details, the corrosion or wear problem, and the service environment, and we will recommend the right process and provide a firm price.