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To weld cast iron with nickel rod, clean the casting to bright metal, drill the crack ends, and run short 1-inch stringer beads with a 99% nickel (ENi-CI) or 55% nickel (ENiFe-CI) stick electrode. Peen each hot bead, skip around the joint so heat never builds up, and let the part cool slowly under a welding blanket.
The rod choice comes down to one question: will you machine the repair? Nickel 99 stays the softest and easiest to machine. Nickel 55 costs less, is stronger and handles thick sections and dirty, high-phosphorus iron better.
This guide covers stick welding only. Amperage numbers come from the Harris (a Lincoln Electric company) technical data sheets for its NIC-L-WELD 99 and NIC-L-WELD 59 electrodes, so start with the range printed on your own rod box.
| Time | 1 to 3 hours of welding, plus several hours of slow cooling |
| Difficulty | Intermediate (you should already run steady stick beads on steel) |
| Tools | AC or DC stick welder, nickel rods, angle grinder, drill, ball peen hammer, heat source, welding blanket |
Nickel 99 vs Nickel 55: Which Rod to Use
Pick Nickel 99 (AWS A5.15 ENi-CI) for thin castings and any repair you’ll drill, tap or mill afterward. Pick Nickel 55 (ENiFe-CI) for thick sections, ductile iron, multi-pass repairs and joining cast iron to steel.
Lincoln Electric’s electrode guide gives the reasons. Its Tech-Rod 99 deposit stays machinable even in single-pass repairs with heavy mixing (admixture) of cast iron into the weld, and it works best on castings with low or medium phosphorus. Tech-Rod 55 welds are stronger and more ductile, tolerate more phosphorus and expand less with heat, which means fewer cracks along the fusion line. The trade-off: with high admixture, a 55 deposit can turn hard and tough to machine.
| Factor | Nickel 99 (ENi-CI) | Nickel 55 (ENiFe-CI) |
|---|---|---|
| Nickel content | About 99% | About 55% (iron balance) |
| Machining after welding | Best; stays soft in single passes | Usually machinable; can harden with high admixture |
| Strength and ductility | Lower | Higher |
| Thick or heavy sections | Fair | Better choice |
| High-phosphorus or dirty iron | Best on low to medium phosphorus | More tolerant |
| Cast iron to steel | Possible | Better choice |
| Cost | Higher | Lower |
Nickel rods use the AWS A5.15 code, so they don’t read like the steel welding rod numbers on a 6011 or 7018. Look for ENi-CI or ENiFe-CI on the box. ENiFe-CI-A is a close variant in the same nickel-iron family.
Nickel Rod Amperage Chart for Cast Iron
Run nickel rods at the low end of their range. Extra amps melt more cast iron into the weld, and that admixture makes the deposit harder and more crack-prone.
| Rod diameter | NIC-L-WELD 99 (ENi-CI) | NIC-L-WELD 59 (ENiFe-CI-A) |
|---|---|---|
| 3/32 in | 50 to 80 A | 50 to 80 A |
| 1/8 in | 80 to 120 A | 70 to 110 A |
| 5/32 in | 110 to 140 A | 100 to 140 A |
| 3/16 in | 130 to 170 A | 130 to 175 A |
| Polarity | AC, DCEP or DCEN | AC or DCEP |
Source: Harris Products Group technical sheets for NIC-L-WELD 99 and NIC-L-WELD 59. Other brands publish slightly different ranges, so the label on your box wins. For most home repairs on brackets, housings and vise bodies, a 3/32 in or 1/8 in rod is the usual pick.
What You’ll Need
- Stick welder (AC, or DC with the polarity your rod allows)
- Nickel 99 or Nickel 55 electrodes, 3/32 in or 1/8 in, kept dry
- Angle grinder with a grinding wheel and a flap disc
- Drill with a 1/8 in bit for stop holes
- Ball peen hammer or a needle scaler for peening
- Propane or oxy-fuel torch, or an oven, for preheat
- Temperature crayons or an infrared thermometer
- Welding blanket or a bucket of dry sand for slow cooling
- Helmet, leather gloves, jacket, and a respirator rated for welding fume
How to Weld Cast Iron With Nickel Rod: Step by Step
These steps follow the same rules you use to prevent cracking when welding cast iron with any process: even heat, short beads, stress relief and slow cooling.
Step 1: Confirm It’s Cast Iron
Grind a small spot. Gray cast iron throws short, dull red sparks and leaves gray, powdery dust. Mild steel throws long, bright yellow streams. If the part is cast steel or cast aluminum, nickel rod is the wrong filler.
Step 2: Clean to Bright Metal
Remove paint, rust, oil and grease from at least 1 inch around the joint. Oil-soaked castings like engine parts and gearboxes hold oil in the pores, so warm the area gently with a torch, let the oil sweat out, and clean again.
Step 3: Drill the Crack Ends
Find the true end of the crack (dye penetrant helps) and drill a 1/8 in hole just past each end. The hole stops the crack from running further when the casting heats up.
Step 4: Grind a V-Groove
Grind the crack into a V with rounded edges, deep enough that the first pass ties into sound metal. On a full break, bevel both halves and tack them back in line.
Credit: www.youtube.com
Step 5: Preheat if the Section Is Thick
Thin castings can be welded cold with nickel rod. Heavy sections need preheat: Harris lists about 400°F for NIC-L-WELD 99 and 400°F to 500°F for NIC-L-WELD 59, and Lincoln calls for at least 350°F preheat and interpass with Tech-Rod 55. Heat the whole part evenly, not just the weld spot.
Step 6: Run Short Stringer Beads
Set the amps near the low end of the chart and hold a short arc. Run a straight stringer bead about 1 inch long, with no side-to-side motion.
Step 7: Peen Each Bead Right Away
Right after each bead, tap it with the rounded face of a ball peen hammer. Light, fast blows stretch the nickel deposit as it shrinks, which takes stress off the cast iron beside it.
Step 8: Skip Around the Joint
Move to a different spot for the next bead, or use a back-step sequence. On a cold-welded part, wait until you can hold your bare hand on the metal beside the weld before you add the next bead.
Step 9: Cool It Slowly
Wrap the finished part in a welding blanket or bury it in dry sand and leave it for several hours. Never quench cast iron in water or blow air on it.
Step 10: Inspect and Finish
Check the fusion line for hairline cracks once the part is cold. Grind out any crack and reweld it with the same short-bead method. Machine or file the repair only after it has fully cooled.
Credit: www.youtube.com
Common Mistakes to Avoid
- Too many amps: more heat means more admixture, harder weld metal and more cracks at the fusion line.
- Long beads: a 6-inch bead pumps heat into one area and the casting cracks beside it.
- Skipping the stop holes: the crack keeps growing ahead of the weld.
- Wide side-to-side beads: stick to narrow stringer beads.
- Using Nickel 55 on a part you must machine after a heavy single pass: the deposit can come out too hard to drill.
- Fast cooling: a cold shop floor or a breeze can crack a good weld an hour later.
Nickel Rod vs Other Ways to Repair Cast Iron
Nickel rod is the go-to for stick welding cast iron because the soft deposit gives a little as it cools. A low-cost steel cast iron rod such as Lincoln Ferroweld (AWS ESt) works on castings you can’t fully clean, but its deposit is hard, can only be ground, and rusts like the casting around it.
If you’d rather braze or fusion weld with a torch, you can weld cast iron with oxy acetylene and a cast iron filler rod, which allows a very slow, even heat cycle.
Safety When Welding Cast Iron With Nickel Rod
- Fumes: nickel electrodes put nickel compounds into the fume, and burning oil from old castings adds smoke. Use local exhaust or a respirator rated for welding fume, and follow the rod’s Safety Data Sheet.
- Burns: a preheated casting at 400°F looks the same as a cold one. Mark it hot and handle it with gloves.
- Fire: oil sweating out of a casting can catch fire. Keep a fire extinguisher close and clear rags and fuel from the area.
- Pressure parts: don’t weld a cracked cast iron gas valve, boiler section or anything that holds pressure. Replace it or use a certified shop.
Frequently Asked Questions
Is 55 or 99 Nickel Rod Better for Cast Iron?
Nickel 99 is better when you must machine the repair or the casting is thin, because its deposit stays soft. Nickel 55 is better for thick sections, ductile iron, multi-pass welds and cast iron to steel, since it’s stronger, more phosphorus tolerant and costs less per pound.
Do You Need to Preheat Cast Iron Before Welding With Nickel Rod?
Thin castings can be welded cold with nickel rod if you use short beads, peening and slow cooling. Heavy sections need preheat. Harris lists about 400°F to 500°F for its nickel rods on heavy cast iron, and Lincoln calls for at least 350°F with Tech-Rod 55.
What Amperage Do You Use for 1/8 Nickel Rod?
Harris lists 80 to 120 amps for its 1/8 inch NIC-L-WELD 99 rod and 70 to 110 amps for the 1/8 inch NIC-L-WELD 59. Start near the low end of the range on cast iron, because extra heat melts more iron into the weld and hardens it.
Can You Weld Cast Iron to Steel With Nickel Rod?
Yes. Nickel 55 (ENiFe-CI) is the usual pick for joining cast iron to mild steel, and ESAB lists its OK NiFe-CI-A rod for that job. Butter the cast iron side first if the joint is thick, keep the beads short and peen each one.
Why Does My Nickel Rod Weld Crack on Cast Iron?
Most cracks come from too much heat in one spot: high amps, long beads or no time between passes. Oil left in the casting and fast cooling are the next causes. Drop the amps, run 1-inch beads, peen every bead, skip around and cool the part slowly.
Final Words
Welding cast iron with nickel rod works when you keep the heat low and spread out. Clean it, drill the crack ends, run short beads at the low end of the amp range, peen and cool slowly.
Choose Nickel 99 when the repair must be machined and Nickel 55 for thick parts or cast iron to steel. Read the amperage and preheat notes on your own rod box before you strike the first arc.
