Mobile TIG Welding for Precision Stainless Applications

Precision stainless work lives or dies on control. The metal is unforgiving about heat input, sensitive to contamination, and quick to reveal sloppy joints with tea-staining or stress cracking. Taking that level of work on the road, with a mobile welder rig and on site welding services, adds variables you don’t face on a shop floor. Wind, uneven power, tight access at a loading dock, a finicky piece of heavy equipment that cannot leave service, or a handrail replacement in an occupied facility, each introduces challenges that separate hobby gear from a certified industrial setup and a technician who has put years into stainless steel welding.

I have spent long days under trailers and long nights on catwalks, TIG torch in one hand and a purge hose in the other, chasing the same outcome: clean, consistent penetration, proper filler deposition, and a heat tint that never crosses into straw or blue. The tools matter, but the habits matter more. This guide distills what actually keeps stainless TIG tidy and repeatable in a mobile context, where you have one truck, one set of cylinders, a generator, and a promise to keep.

Where mobile TIG makes the difference

Not every project justifies TIG in the field. MIG, or a stick rod, will run faster and tolerate more wind. But there are stainless cases where TIG is the right call, even when you roll up in a truck welding rig. Food and beverage lines want crevice-free welds inside the pipe. Pharmaceutical and dairy systems need purge quality roots with no sugar. Architectural railings and gates ask for fine control on thin material, invisible joints, and a finish that blends in daylight. Marine hardware and aluminum welding on a dock or tender often pairs TIG for thin sections with MIG on thicker brackets. When repair windows are short, like an emergency welder call on a loading dock conveyor or a restaurant’s steam kettle, TIG gives you finesse without spatter cleanup, and it can reach into corners where a MIG gun is clumsy.

I still bring MIG for stainless structural additions, tacking sections quickly before switching to TIG for visible seams. Stainless often lives next to carbon steel in industrial settings, and a mobile welder who can run both processes, plus stick for dirty farm steel or weathered fence welding, keeps options open. Even on wrought iron fencing and railings, TIG earns its keep repairing cast scrolls or delicate collars.

The truck, the power, and the quiet details that save a job

A mobile TIG setup starts with predictable power. I keep a generator with a true sine wave output and at least 10 kW continuous, so the inverter TIG holds a steady arc at low amps. Some machines tolerate rougher power, but the arc becomes twitchy, especially in pulse. Oil changes and fuel filters are not glamorous, yet they are why the arc stays stable at 35 amps when you are welding a 0.035 inch stainless fascia.

Alongside power, gas management defines mobility. I stock two argon cylinders and one tri-mix for stainless MIG, with quick-connect manifolds. A small nitrogen bottle rides along for pressure testing and purging dead legs when gas is expensive. For pipe welding, I bring foam dams and inflatable bladders in a Pelican case, plus a flux paste for rare cases where a full purge is impossible and the client accepts the trade-off because access is impossible. Portable welder rigs get cramped, so I bundle lines with Velcro straps and color-code gas, water, and power. If you have ever tripped over a water line and put a tiny kink in it, then chased overheating at the torch for an hour, you learn to route hoses with the same care you give an X-ray weld.

I carry two torches: a small 9 air-cooled for lighter work and a 20 series water-cooled for continuous duty. Even on mobile jobs, the water-cooled torch pays for itself. It keeps your hand cool running 100 to 130 amps on 3/16 stainless, and it keeps the cup stable so gas coverage does not wobble. For aluminum work on site, I add an AC square-wave machine or a multi-process inverter, and a dedicated set of clean brushes and dedicated stainless/aluminum prep tools. Cross-contamination ruins surfaces faster than bad filler choices.

Consumables tell on you. Gas lens cups from 4 to 12, a couple of large BBW style Pyrex cups, 2 percent lanthanated tungsten in 1/16 and 3/32, and stainless wire in 308L, 309L, and 316L cover most needs. If you weld on carbon to stainless, like adding a stainless handrail base to a mild steel plate at a loading dock, 309L filler protects against dilution. Keep 0.035 and 0.045 solid wire for stainless MIG in case wind or time constraints push you that way. Wipe packs of acetone or isopropyl, stainless-only wire brushes, and new flap wheels labeled for stainless ensure you never drag iron into a visible surface. I have turned down rush work rather than contaminate a stainless panel with a dirty grinder and eat the rework later.

Stainless behaves differently in the field

Stainless expands, hangs on to heat, and displays every mistake with color bands. In the field, those traits amplify. The base metal often has seen service, so it contains chlorides, grease, or phosphates that sabotage your arc and call for deeper cleaning. If you get purging wrong in a pipe, the root can sugar, growing chromium-depleted scale that cracks later. That is not just cosmetic, it can leak or trap product in sanitary lines. Even on architectural railings and gates, sugared backsides can rust and stain stonework in a season.

Shielding gas coverage is the mobile TIG welder’s air supply. Wind moves smoke and gas. I carry a welding screen and spring clamps to throw up a windbreak in minutes, and a pair of small magnetic ground sheets to block drafts around floor-level joints. Upping flow from 20 to 35 cubic feet per hour does not cure wind, and it often creates turbulence. The fix is physical shelter, proper cup size, and a steady torch angle. A gas lens and a number 8 or 10 cup, with 3/8 to 5/8 inch stick-out on a sharpened 3/32 tungsten, will ride light breeze if you keep the arc tight. On mirror-finished cladding, I add a trailing shield with a small line reducer to 10 to 15 CFH, so the heat tint shrinks to a champagne hue that pickles off in one pass.

Heat control is the second pillar. I like to set a primary amperage slightly above the calculated value, then ride the foot pedal to keep the puddle small. For 0.065 inch 304 tube, starting at 55 to 65 amps with a 1.5 pulses per second, 30 to 40 percent peak time, and 30 to 50 percent background current gives a rhythm that controls heat without starving the puddle. On 3/16 plate in an industrial bracket repair, I turn off pulse and run 95 to 110 amps, dab 1/16 filler steadily, and move. Anything that keeps you in and out quickly reduces the heat-affected zone and the blue halo that clients hate to see.

Purging real-world stainless joints

Purge is not optional for sanitary pipe welding and is smart on many structural welds when the backside matters. In a brewery retrofit, I often see 1.5 inch schedule 10 pipe with existing runs that cannot be fully disassembled. I isolate with foam dams 6 to 10 inches each side of the joint, feed argon at 20 CFH until an oxygen meter reads under 0.1 percent, then drop flow to 10 to 15 CFH for the weld. If I cannot meter, I give it three to five volume changes based on the enclosed space, then test with a lighter at the vent for gentle outflow. It takes patience. Too much flow whips up turbulence and drags in air from the vent side. Too little leaves the backside dull and grainy, a dead giveaway that chromium is burning out.

On field-fit couplings, I always drill a pinhole on the low side for a weep vent, keep the purge hose on the high side, and tape the joint neatly. I have welded in a tank farm where tape adhesive ruined the first pass as it off-gassed. Since then, I use high-temp aluminum tape or Kapton and clean it before I strike. On larger pipe welding runs that must stay in operation, inflatable purge bladders with a bypass line let you purge a short section while the process flows minimal gas. Plan those jobs with operations staff so no one surprises you with a pressure spike that pops a dam into your fresh root.

Field joints, fit-up, and how to keep stainless straight

Fit-up consumes half the job when the work happens at a site. Pipes rarely align perfectly. Railings are out by a quarter inch because the original fabricator drove a wedge into a bent post and hammered it straight. Heavy equipment frames are twisted from years of impacts. When the metal is stainless, you cannot bulldog it with heat the way you might on carbon. You will warp a panel or print a twist down an entire handrail.

Dry-fit matters. I shim with brass and stainless feelers, clamp with non-marring jaws, and tack strategically. Short, cool tacks on opposing sides balance pull. If a gap exists, I bevel to 30 to 37.5 degrees, rather than bridge it with filler. Gaps invite sagging and color. On thin architectural angles, I back the joint with copper bars where possible, even if it means drilling a temporary screw hole to hold the copper support. One neat trick for square tube railings: tack inside corners first, where any shrink will pull inward and hide, then dress external joints with TIG to keep faces flush.

On more structural stainless repairs, like a cracked loading dock bumper mount or a broken equipment guard, stainless’s lower thermal conductivity bites you. Heat piles up fast. I keep a spray bottle of distilled water and cool between passes. Not a quench, just a mist to drop temperature below 150 F so the next bead starts clean and the heat tint stays light.

Process choice: TIG, MIG, or both

TIG owns the edge cases of thin material, purge-critical pipe, and cosmetic seams in visible locations. MIG shines when wind rises or the joint is longer than your client’s patience. In the field, hybrid work is common. For a stainless channel reinforcement on a trailer, I might root with TIG to lock penetration, then switch to MIG with tri-mix gas to fill and cap quickly. If wind forces the choice, I will build a more robust windbreak or reschedule, rather than smear stainless spatter over finished surfaces and spend hours grinding.

Stick has its place too. If you are repairing a gate hinge on a ranch fence in the cold, dragging 200 feet of leads, a 309 stick rod runs on a portable welder all day and fuses stainless to carbon without elaborate prep. It is not pretty, but some jobs are utility-first. Save TIG for the last pass or for the hinge pin sleeve, where alignment matters.

Certified work, inspection, and traceability

A mobile welder advertising certified AWS credentials needs to live up to the paperwork on site. On structural stainless connections, inspectors may ask for WPS and PQR documents that cover base materials, filler, positions, and parameters. I keep a binder and digital copies in the truck, along with mill certs for common fillers like ER308L, ER309L, and ER316L. When a job includes industrial stairs and railings tied into a mezzanine, I have been asked to weld test coupons on site in the vertical position for the inspector’s assurance. It feels like a detour, but it builds trust and speeds final acceptance.

Traceability matters for sanitary work as well. In a dairy, I label every spool and elbow I fit, record heat numbers for 316L tubing, and document purge levels if the QA manager requests it. You do not need to overcomplicate a small pipe repair, but consistent notes protect both sides if a leak appears months later.

Surface prep, passivation, and keeping stainless stainless

Stainless owes its corrosion resistance to a thin chromium oxide layer that forms cleanly only on a clean surface. The fastest way to spoil it is to grind with a wheel that once touched carbon steel. That embeds iron and sets up rust blooms that show up as brown freckles. I carry a set of stainless-only abrasives in blue bins and replace them often. For prep, acetone and lint-free wipes remove oil. For a heavy degrease on food service gear, I use a citrus-based cleaner, rinse, dry, then wipe with alcohol just before welding.

After welding, color tells the story. Straw to light gold near a bead usually wipes away with a non-woven pad and a passivation gel. Blues and purples demand more attention. On architectural work where finish is king, I use an electrolytic weld cleaner with a phosphoric or sulfuric mix to restore the oxide layer without scratching. On industrial pieces that will be painted or hidden, an abrasive cleanup and a brush are sufficient, but I still avoid overheating and heavy grinding. If you grind stainless too aggressively, you can smear metal and trap contaminants. Short strokes with fresh discs preserve the grain.

Managing heat tint on thin sections and polished surfaces

When you weld a polished 304 fascia or a mirrored elevator panel, no one cares how strong it is if they can see the halo. Control starts before the arc. Fit tight, run a larger gas lens cup, and consider a trailing shield. Pulse helps, but it is not magic. What matters is consistent travel speed and small dips. I sharpen a 1/16 tungsten to a long taper, step down to 0.035 filler if fillet size permits, and run amps just high enough to make a fluid puddle without sitting still.

I have done repair passes on restaurant fixtures where you cannot get behind the metal. In those cases, a heat sink makes or breaks the blend. A chilled copper bar clamped behind the joint draws heat away, and a gentle breeze of argon from a third hand keeps the surface shielded for a second after you break the arc. If color still creeps, stop, cool the area, and start again a half inch back with a short overlap. Trying to muscle through with rising heat just blooms more oxide.

Aluminum and stainless on the same truck

Many mobile calls bundle stainless jobs with aluminum welding. A cracked marine ladder in the same visit as a stainless grab rail. A loading dock lip that needs aluminum MIG, followed by a stainless bollard repair. The key is mental discipline about cleanliness and segregation. I keep aluminum brushes and dedicated nozzles in a red roll, stainless in blue, and I never cross them. For AC TIG on aluminum, I run a separate machine or, if using a multiprocess TIG, I blow out the torch and lines with argon, swap cups, and change gloves. It takes five minutes and saves a headache later when a TIG pass on stainless sputters from a stray bit of oxide dust.

Field ergonomics, safety, and the pace of real jobs

A shop allows perfect posture and fixtures. The field does not. You might weld a pipe joint above your head at the back of a refrigeration plant while kneeling on grating. Good body mechanics still matter. I set blocks or a knee pad, get my wrist supported, and position the pedal or a thumb control so I can modulate without shaking. Practice with a torch-mounted rocker pays off when your foot cannot reach.

Safety often collides with schedule. Clients want the line back up. Stainless grinding dust lingers, and TIG silently bakes oxygen in a tight corner. I keep a portable fan to clear fumes, a gas monitor for tanks and pits, and insist on lockout for equipment repairs. It is not negotiable. On emergency welder calls, the pressure to hurry is real, but a burn or a flash in a hurry costs more time than a setup done right. When a client sees you methodically tarp a work area, tape off polished surfaces, and set a fire watch, they understand you are protecting their property as much as your weld.

Typical mobile TIG stainless scenarios and how to approach them

Brewhouse pipe repair: A pinhole on a 2 inch 304 line. Isolate 18 inches with foam dams, purge to under 0.1 percent O2, feather the area with a fine disc, and TIG a small patch with 308L, using pulse to keep the heat minimal. Brush, passivate, document.

Restaurant handrail modification: Recut four posts to new height. Protect floors, clamp a sleeve to keep the cut square, TIG new caps with 316L for better chloride resistance, blend only the cap edges, then electrolytically clean the heat tint to keep the finish bright.

Loading dock bracket replacement: Stainless guard tore free at the anchors. Remove hardware, dress the frame, add a 3/16 304 backer plate, tack with TIG for fit, switch to MIG with tri-mix for speed, then TIG the exposed edges for cosmetic uniformity. Tie back into concrete with fresh anchors and document torque.

Trailer fairing repair: Thin stainless skin cracked along a seam. Back the joint with copper, clamp gently, TIG with a small gas lens at 35 to 45 amps, skip weld to control warp, cool between passes, then passivate. If vibration caused the crack, add a small reinforcement tab inside where invisible.

Gate latch upgrade on stainless and carbon mix: Existing mild steel post, stainless latch. Clean both thoroughly, use 309L filler with TIG to bridge the metals, keep heat tight to the stainless side, and seal with a bead that sheds water. Optional primer for the carbon steel around the weld to slow corrosion.

When to say no, or not yet

A mobile welder builds reputation as much by what they decline as by what they accept. If the wind at a coastal site hits 20 mph with gusts, a purge-critical stainless job will fight you. If the client will not allow water shutoff for a pipe welding repair and the line drips steadily, you will never keep the root clean. I have rescheduled a job after two hours of struggle rather than produce a repair that would fail in six months. Explain the technical reasons. Offer a temporary clamp or a bypass. Most clients respect honesty backed by clear options.

Pricing, scope, and avoiding scope creep on stainless

Stainless TIG work runs slower than carbon MIG and consumes more consumables. Quote with that in mind. Include time for purge setup, cleaning, and post-weld finishing. Spell out what finish level the client expects: brushed, blended, mirror, or just structurally sound. Define who provides access, power, and shutdowns in an industrial setting. When a site adds “one more little weld” on aluminum after you have set up for stainless, you can accommodate, but keep track of the change. A clear scope prevents friction when you do meticulous work that takes the time it takes.

The value of versatility in the field

Mobile stainless specialists who also handle pipe repair, wrought iron fencing fixes, and structural repairs keep a full calendar. A day might start with a sanitary TIG patch before breakfast, a midday fence repair, then an after-hours industrial guard rebuild. Having TIG, MIG, and stick in the truck, with fillers for stainless and aluminum, means you solve more problems in one trip. The trick is maintaining standards. Do not let a rough job bleed into a fine one. Swap consumables, clean your station, and treat the next stainless pass like you are under an inspector’s eye.

Quick field checklist for stainless TIG success

• Dedicated stainless prep tools and abrasives, never cross-used on carbon steel.
• Predictable power and gas management, including purge gear and a windbreak.
• Proper consumables: gas lens cups, lanthanated tungsten, and the right filler (308L, 309L, 316L).
• Heat control habits: fit-up, pulse when helpful, water-cooled torch for comfort.
• Post-weld cleanup: brush, electrolytic or chemical passivation, and documented QA when required.

Final thoughts from the road

Precision stainless TIG on site is less about glamorous beads and more about discipline in hard conditions. A certified mobile welder who treats every joint as if it will be photographed, who understands when to use TIG, MIG, or stick, and who respects purge, cleanliness, and heat input, delivers results that hold up. Whether you are patching a dairy line, adding industrial railings, repairing equipment on a loading dock, or tuning a stainless gate latch on a windy jobsite, the fundamentals do not change. Control what you can, mitigate what you cannot, and leave behind joints that do not advertise themselves with stains or failures.

The best compliment is a call you do not get, months later, because the weld did its job silently. The second best is the next call, to a new site, from someone who saw your work and wants the same level of care.

On Call Mobile Welding

917 J Pl Suite 2, Plano, TX 75074

(469) 750-3803