Welding Electrodes

What sets stick electrodes apart

Shielded metal arc welding (SMAW) uses a coated rod that is both the filler metal and, as the flux coating burns, the source of shielding gas and slag that protects the weld pool. That is what makes it the standard shipboard repair process: no gas cylinder, no wire feeder, nothing but a welding set, cables, a rod and an electrode holder. Against MIG/MAG wire processes it deposits weld metal more slowly and demands more operator skill to maintain arc length and travel speed, but it tolerates wind, damp surfaces and awkward positions far better, which is exactly the environment most at-sea repairs happen in.

Welding electrode (SMAW stick electrode) — Side view of a stick welding electrode showing the core wire running inside the flux coating, the bare end gripped by the electrode holder, the flux-covered arc end, and a cross-section through the rod.

Main components / classification

Core wire and flux coating

The core wire supplies most of the deposited metal; the flux coating generates shielding gas, forms a protective slag layer, stabilises the arc and can add alloying elements. Coating type, rutile, basic/low-hydrogen, or cellulosic, determines arc characteristics, weld appearance and, critically, hydrogen content in the weld.

Classification marking

Electrodes are marked to a recognised classification system, such as AWS A5.1 for carbon steel, indicating tensile strength, welding position suitability and coating type - for example an E7018 rod is a common low-hydrogen electrode giving roughly 70,000 psi tensile strength, weldable in most positions.

Packaging and storage condition

Low-hydrogen (basic) electrodes are supplied in sealed containers and must be kept in a heated holding oven once opened, since they absorb atmospheric moisture readily; cellulosic and rutile types are far less sensitive.

Selection and sizing

The right electrode is chosen to match the parent steel, not chosen for convenience:

Match tensile strength and chemistry to the parent plate - a mismatch can leave a weld weaker or more brittle than the surrounding steel
Coating type versus joint condition - basic/low-hydrogen for higher-strength or thicker structural steel where hydrogen cracking is a risk, rutile for general-purpose repairs, cellulosic where deep penetration on pipe root passes is needed
Diameter matched to plate thickness and welding position - larger diameters deposit faster but are harder to control out of position
Storage and redrying capability on board - a low-hydrogen electrode that has absorbed moisture should be redried before use or it defeats its own purpose

Typical faults

Fault	Cause	Consequence
Hydrogen-induced cracking	Damp or improperly stored low-hydrogen electrode used without redrying	Delayed cracking in the weld or heat-affected zone, sometimes days later
Porosity	Rusty, oily or wet parent metal, or damaged flux coating on the rod	Weak, porous weld requiring gouging and rewelding
Wrong electrode for parent steel	Using a general-purpose rod on high-strength or unusual alloy steel	Weld metal mismatch, reduced joint strength, possible failure under load
Poor fusion	Wrong amperage setting or excessive travel speed for the rod diameter	Lack of penetration, weak joint that looks acceptable on the surface

What to look for in a supplier

Current classification certificates and, where the ship trades under a class-approved welding procedure, class-approved electrode grades
Sealed packaging with visible manufacture date, especially for low-hydrogen types
A range of diameters and coating types covering both structural steel and general repair work, not just one general-purpose grade
Consistent batch quality, since a change in supplier mid-repair can change arc behaviour the welder has to adjust to

Keep low-hydrogen electrodes in the holding oven once the tin is opened - a rod left out overnight on a humid deck can pick up enough moisture to seed a crack that only shows up after the weld has cooled.