Welding: what to know

What the job involves, what changes the price, and what to ask a pro.

What welding is

Welding joins metal parts by melting and fusing them, for repairs such as railings, trailers and gates, or for new fabrication. A welder chooses the process, the filler and the heat to suit the metal, the thickness and the load the joint will carry. Welding is one of the trades where the wrong process or a poor joint can fail without warning, so the choice of welder matters.

Signs you need it

  • A metal railing, gate hinge, trailer frame or bumper has cracked, broken or pulled loose at a weld or a joint
  • You need a metal part repaired or rebuilt, and the original shape or strength must be restored
  • A trailer, equipment frame or farm implement has a broken bracket, a worn hitch or a cracked crossmember
  • You want a new gate, rack, bracket or railing made from steel, aluminum or stainless
  • A cast iron or aluminum part has broken, and it needs a repair method that suits that metal

What the pro does

  • The welder identifies the metal type, the thickness and the load, and checks whether the part is coated, painted or galvanized
  • They clean the joint and remove paint, rust, grease and coatings from the area that will be welded
  • They choose the process, such as MIG, TIG or stick, and the filler that matches the base metal and the job
  • They tack the parts in place, check the fit and the alignment, and control the heat to limit distortion
  • They complete the weld with the bead size and the penetration the joint needs, and check it for cracks, porosity and undercut
  • They dress the weld and finish the part, and tell the customer what load and use the repair is suitable for

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Metal type, since steel, stainless, aluminum and cast iron each need a different process and skill
  • Thickness of the material and the length of the joint to be welded
  • Condition of the part, including rust, paint, cracks, distortion and prior weld repairs
  • Access to the joint, whether the part is on a vehicle, in place on a structure or must be taken off
  • Whether the joint must meet a specific strength or inspection requirement
  • Fabrication versus repair, with the time for design, cutting and fitting included
  • Finish required after welding, such as grinding, painting or galvanizing

What a written quote should spell out

  • Metal type and thickness, with the process and the filler the welder will use
  • Scope of the repair or fabrication, with the joints to be welded listed
  • Preparation included, such as removing coatings, cleaning and fit-up
  • Post-weld finish, such as grinding, painting or coating
  • Whether the part must come off the vehicle or structure, and who handles that
  • Any inspection or testing included, and what the welder does about cracks found after the repair

Questions to ask before you hire

  • What metal is this, and which process will you use on it?
  • Will the repair carry the load it carried before, and how do you judge that?
  • Do you remove the paint and coatings before welding, and how do you protect the nearby parts?
  • Is this a structural repair, such as a trailer frame or a load-bearing bracket, and do you follow a specific code?
  • Will you check the weld for cracks or porosity before you hand it back?
  • What is your warranty on the weld, and does it cover a repeat failure at the same joint?
  • Can you show me photos of similar repairs on the same metal type?

Red flags

  • They weld a cast or aluminum part with the same process and filler used on steel, without explaining why
  • They will not say what metal the part is made from before they quote
  • They do not remove paint or galvanizing from the joint before welding, and do not mention the fume risk
  • They will weld a trailer hitch, a load-bearing bracket or a structural joint without asking how it will be loaded

What you can do yourself

Do not weld structural parts, trailer hitches, lifting points, braced members or any part that holds weight or carries people. Do not weld near fuel tanks, gas lines, painted or galvanized metal without proper ventilation, or any pressurized part. Welding produces fumes, bright light and sparks that cause serious injury, so take the job to a qualified welder unless the work is purely decorative and well clear of any load or hazard.

Licenses and permits

Welding is commonly done without a state license for general repair, but welders doing structural, pressure or inspected work often need a welder certification and may need a contractor registration. Check with your state or local licensing agency and your local building department for the certification and permit rules that apply to your job.

Welding questions

Can any welder fix a trailer frame?

A trailer frame carries load and affects braking and steering. Ask the welder about their experience with trailer frames, the process they will use and whether they will check the weld after the repair. A weld that looks good can still fail if the metal or the process is wrong.

Why does the welder need to know the metal type?

Each metal behaves differently under heat. Steel, stainless, aluminum and cast iron need different processes, fillers and preheat. Using the wrong one can produce a weak joint that cracks later.

Should I remove a part before it is welded?

It depends on the part and the access. Removing it lets the welder control the heat and clean the joint properly. Ask the welder whether the part must come off and how it will be protected if it stays in place.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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