Few issues are more frustrating for welders than a 7018 rod that repeatedly sticks to the base metal. This problem not only disrupts workflow but also risks weakening the weld with cold laps or incomplete fusion. 7018 rods, while prized for their strength and crack resistance, are more prone to sticking than simpler rods like 6013 due to their low-hydrogen coating and specific operational requirements. The root causes typically boil down to three key factors: improper amperage, poor rod condition, and flawed welding technique.
Incorrect amperage is the most common culprit. 7018 rods require a precise balance of heat to maintain a stable arc-too little amperage, and the rod can't melt quickly enough, causing it to stick. As a low-hydrogen rod, 7018 has a denser coating that needs sufficient heat to ionize properly and sustain the arc. For example, a 1/8-inch (3.2 mm) 7018 rod needs 90–160 amps to function; if the welder sets the machine to 70 amps, the arc will sputter and die, leaving the rod stuck to the metal. Conversely, excessively high amperage can cause the rod to overheat and melt too fast, but sticking is far more likely with under-amperage. Welders should always match the amperage to the rod diameter (as outlined in welding charts) and adjust based on position-vertical or overhead welding may need slightly lower amperage than flat welding, but never so low that the arc can't sustain itself.
Poor rod condition is another major cause. 7018's low-hydrogen coating is hygroscopic, meaning it absorbs moisture from the air. If rods are not preheated and stored properly, moisture in the coating disrupts arc stability. Moisture causes the arc to flicker or extinguish, increasing the chance of sticking. Even slightly damp rods may not produce a steady arc: the moisture breaks down during welding, creating uneven gas release that destabilizes the arc. Additionally, rods that are old, damaged, or have a cracked coating can't conduct current uniformly, leading to intermittent sticking. To avoid this, 7018 rods must be preheated to 350°F (175°C) for 1 hour to remove moisture, stored in a rod oven at 250–300°F (120–150°C) until use, and never left exposed to humid air for more than 4 hours (or 1 hour in high humidity).
Welding technique also plays a critical role. 7018 requires a steady, slightly longer arc than rods like 6013. A common mistake is holding the arc too short, which reduces the distance between the rod and the base metal, increasing the risk of contact. When the arc length is too short, the molten metal bridges the gap, sticking the rod. Welders new to 7018 may also hesitate to maintain consistent travel speed: pausing too long in one spot cools the arc, while moving too fast starves the pool of heat. Both errors can lead to sticking. Proper technique involves striking the arc with a quick "scratch" or "tap" (avoiding prolonged contact), maintaining a 1/8–1/4 inch arc length, and moving steadily to keep the weld pool fluid.
Base metal preparation can exacerbate sticking issues. If the base metal is dirty, rusty, or coated with oil, paint, or mill scale, the arc will struggle to penetrate evenly. Contaminants act as insulators, disrupting current flow and causing the arc to falter. For example, a rusty surface may conduct electricity unevenly, leading the rod to stick when it contacts a particularly thick rust patch. Welders should always clean the base metal with a wire brush or grinder to remove oxides and debris before starting-this ensures a consistent path for the arc and reduces sticking.
Machine settings beyond amperage can also contribute. 7018 performs best with direct current reverse polarity (DCRP), where the electrode is positive. Using alternating current (AC) or direct current straight polarity (DCSP) can weaken arc stability, making sticking more likely. AC machines, in particular, may struggle to maintain a steady arc with 7018, as the current alternates direction, causing momentary dips in heat that increase sticking risk. Welders should check that their machine is set to DCRP unless using a specialized AC-rated 7018 rod (rare and often marked as such).
In summary, 7018 rods stick most often due to under-amperage, moisture-absorbed or damaged rods, short arc length, dirty base metal, or incorrect current polarity. The solution involves matching amperage to rod size, preheating and storing rods properly, maintaining a steady arc length, cleaning the base metal, and using DCRP. With these adjustments, the rod will melt smoothly, the arc will stay stable, and sticking will become a rare occurrence-allowing welders to leverage 7018's strength without frustration.
