77 Cast Iron Welding Rod is a premium high-strength electrode designed specifically for welding all types of cast iron, including clean gray cast iron, contaminated castings, and previously welded repairs. Engineered for durability and machinability, 77 produces a smooth, dense, porosity-free weld that eliminates the need for preheating or special cooling techniques in most cases.
This cast iron welding rod is the top choice for professional and hobby welders alike who want clean, strong, and reliable repairs on cracked or broken castings.
Why Choose 77 Cast Iron Welding Rod
High Strength and Machinability: 77 creates a high-tensile-strength weld that’s easily machinable, unlike typical nickel rods that produce hard, brittle deposits.
Crack-Resistant Formula: The advanced alloy composition allows the weld to stretch and move with the parent metal during heating and cooling, preventing stress cracks.
No Preheat Required: 77 eliminates the need for preheating in most applications, saving time and simplifying repairs.
Porosity-Free Results: Designed to penetrate contaminated or oil-soaked cast iron surfaces and produce dense, defect-free welds.
Clean, Smooth Appearance: 77 lays down evenly, producing flat, uniform welds with minimal spatter.
Strong Bond on Old Repairs: Ideal for re-welding or repairing previously brazed or welded cast iron joints.
Cross-Compatible System: For burnt or heavily contaminated cast iron, start with 72 Cast Iron Welding Rod to anchor into the base metal, then finish with 77 for strength and appearance. For nodular, ductile, or malleable cast iron, use 75 Cast Iron Welding Rod for optimal ductility and color match.
Learn How to Repair with 77 Cast Iron Welding Rod – Complete Video Series
Kit Includes:
1/2 lb
3/32″ Diameter: 14 rods 12 inch length
1/8″ Diameter: 7 rods, 14 inch length
5/32″ Diameter: 4 rods, 14 inch length
1 lb
3/32″ Diameter: 28 rods 12 inch length
1/8″ Diameter: 14 rods, 14 inch length
5/32″ Diameter: 9 rods, 14 inch length
5 lb
3/32″ Diameter: 168 rods 12 inch length
1/8″ Diameter: 84 rods, 14 inch length
5/32″ Diameter: 54 rods, 14 inch length
Shelf Life and Storage
Store 77 Cast Iron Welding Rods in a dry area at room temperature. Keep rods sealed in their original packaging or an airtight rod tube to prevent moisture absorption. When stored properly, the electrodes maintain full performance and weld quality indefinitely.
How to Use 77 Cast Iron Welding Rod
Prepare the Metal: Clean the repair area to remove oil, dirt, paint, and grease using a grinder, wire brush, or suitable solvent.
Choose the Correct Amperage: Use the recommended amperage range for the rod diameter. Start on the lower end and adjust as needed for penetration.
Short Arc Technique: Maintain a short arc length for better control, penetration, and bead appearance.
Peen Each Bead: After each pass, lightly peen the weld while it’s still hot to relieve stress and prevent cracking.
Allow to Cool Naturally: Avoid quenching or forced cooling; let the weld air-cool slowly.
For Heat-Affected Cast Iron: Begin with 72 Burnt Cast Iron Welding Rod to anchor into the parent metal, then overlay with 77 for a machinable, finished surface.
For Nodular, Ductile, or Malleable Cast Iron: Use 75 Cast Iron Welding Rod for proper expansion characteristics and a clean color match.
Common Applications
Repairing cracked or broken engine blocks and heads.
Restoring cast iron machine bases, housings, and manifolds.
Welding gearboxes, pump housings, and compressors.
Fixing heavy castings and structural cast components.
Rebuilding cast iron tooling, vises, and frames.
Repairing oil-soaked or previously welded castings.
What Our Customers Are Saying About 77
It was amazing how nicely the 77 flowed with no splattering and popping as experienced in prior cast iron welding repairs. We did not take time to go for a real pretty weld, being more concerned with getting a good, deep penetration weld for maximum strength on this cast iron mounting bracket for the heavy sanding head for a Craftsman 6×48 belt sander in which this part was no longer available, thus rendering it useless until along comes Muggy Weld 77!!! Now we will have a much used, valuable shop tool again available for regular use. Thank you kindly for your great neighborly customer service. — Jim Farley, Gen. Mgr.
In my welding career, I’ve done a fair bit of cast iron repair. After hearing about your product, and watching several videos online. I purchased a bunch of your 77 rods. I had a job modifying a steady rest, that included welding the head to a newly fabricated mild steel base. To say that I am extremely impressed and pleased with your product, is a definite understatement. It flows like warm butter. I wish I knew about your rods a long time ago. — Edward Joskow
I just welded a small block Chevy 400 engine with a broken ear on the starter mount. The engine was sitting on a 3 wheel engine stand and fell over, breaking the mount. I placed a mild steel bolt in the broken mounting hole and built the whole corner back up, then I removed the bolt and re-tapped the bolthole with no problem. It’s looking pretty good. Your 77 welding rods are better than anything I’ve tried in the past. — Bob Carpenter
I received the 77 Cast Iron Rods today. I just fixed a BMW Mini Cooper block that swallowed two piston rods and busted the block. It took me about a half hour to mend the two holes, and I can’t even tell it was ever cracked open. Great Stuff! Saved me a bunch of $$ Thanks! — Frankie Olthoff
Frequently Asked Questions
Do I need to preheat cast iron before using 77?
In most cases, no preheat is required. However, for very large or thick sections, preheating to around 400°F may help reduce stress.
Can 77 be used on oil-soaked or contaminated cast iron?
Yes. 77’s special alloy formulation is designed to bond through light surface contamination and produce porosity-free welds. For heavily contaminated or burnt cast iron, use 72 Cast Iron Welding Rod first to anchor into the base, then overlay with 77.
Can I use 77 on nodular or ductile cast iron?
For best results on nodular, ductile, or malleable cast iron, use 75 Cast Iron Welding Rod. It provides the necessary ductility and color match for those materials.
Is 77 machinable?
Yes. 77 produces a machinable deposit that cuts cleanly without chipping, unlike hard nickel rods.
What polarity should I use?
Use DC reverse polarity (electrode positive) for best results.
Can 77 be used for multiple repairs on the same part?
Yes. 77 is ideal for repairing previously welded or brazed cast iron areas without cracking or porosity.
Summary
77 Cast Iron Welding Rod is the proven solution for strong, machinable, and crack-free welds on all types of cast iron. Its unique formulation eliminates the need for preheating in most cases and produces smooth, dense, professional-quality welds every time.
For the best results on complex cast iron repairs, pair 77 with 72 for contaminated castings and 75 for nodular, ductile, or malleable cast iron. Together, these rods provide the most complete system for cast iron repair and fabrication available.
CALIFORNIA PROPOSITION 65: WARNING: This product contains chemicals including [Nickel], which are known to the State of California to cause cancer. For more information, go to www.P65Warnings.ca.gov
77 is a premium electrode that produces welds which are high strength, crack resistant, and porosity free when applied to a wide variety of cast irons. The special tri-metal core wire has a high current carrying capacity and the specially designed coating converts the impurities of the base metal into slag instead of being trapped in the deposit. The high deposition rate creates an extremely narrow heat affected zone– a feature suitable for all weldable cast irons requiring post weld machining. 77 cast iron welding rods are softer than nickel rods, and have unique properties that allow the cast iron welds to stretch and elongate up to 300 percent more than other rods, which helps prevent the base metal and weld from cracking in the process. Key Features:
High efficiency weld metal transfer eliminates electrode overheating
Crack-resistant formula eliminates the need for pre-heating or special cooling
Ideal for heavy machinery, trucking, bus lines, automotive, marine, and RVs
Repair cast iron exhaust manifolds, engine blocks, industrial machines and more
Note: Guide the electrode at a steep angle, keeping the arc length short. Use short staggered
