Cast iron does not accept a weld the way steel does. Heat it and the carbon at the edge of the pool reacts; cool it and that edge turns into something harder than the casting around it. The repair then fails in one of two ways — it cracks, or it survives and cannot be machined. ENi-CI exists to avoid both outcomes, and it does so by not being a steel electrode at all.
| Classification | AWS A5.15 ENi-CI · ISO 1071 E C Ni-CI 1 · GB/T 10044 EZNi-1 (trade designation Z308) |
|---|---|
| Core wire / coating | Commercially pure nickel core; graphite-type, strongly reducing coating |
| Deposit chemistry | Ni 90% min (typical 94–95%) · C ≤2.0 · Si ≤2.5 · Mn ≤1.0 · S ≤0.03 · Fe ≤8.0 |
| Typical deposit properties | Tensile 240–390 MPa · elongation 3–6% · hardness 120–175 HB · fully machinable |
| Current | AC or DC+ (electrode positive). DC+ is preferred where the supply allows it, because shallower penetration means less base-metal dilution. |
| Positions | Flat, horizontal, vertical and overhead at reduced current; flat for fill passes |
| Standard diameters | 2.5 / 3.2 / 4.0 / 5.0 mm — cut length and pack format to order |
The failure mode of a cast iron repair is decided in a zone a fraction of a millimetre wide — the boundary where the weld metal meets the casting. A steel electrode puts iron into that boundary. The casting's carbon migrates into it, and on cooling it forms martensite or a white-iron structure: hard, brittle and effectively unmachinable. A file skates across it. A drill burns. Cracks start there weeks later, usually after the part has gone back into service.
A nickel deposit does not do this. Nickel holds carbon in solid solution instead of forming hard carbides, so the boundary stays soft and the deposit stays austenitic and ductile. Three practical consequences follow, and all three are why buyers specify this electrode rather than a cheaper one:
The repair can be finished with normal tooling. Milling, drilling, tapping and grinding behave predictably, which matters on a guideway, a bearing seat or a gasket face where the weld is only an intermediate step.
The heat-affected zone stays machinable. This is the part buyers forget to ask about until a second repair fails. It is not the weld that resists the cutter, it is the strip beside it.
The deposit yields instead of cracking. Low elongation sounds like a weakness in a data sheet. In a restrained casting it is the mechanism that keeps the repair intact while the part cools.
Nickel is the expensive part of this product, and pretending otherwise would be dishonest. ENi-CI is specified where the alternative is scrapping a casting that has already absorbed machining time, not where a general-purpose electrode would do.
| Application | What the repair has to survive |
|---|---|
| Cylinder heads, engine blocks and manifolds | Thermal cycling, bolt-load restraint, and a sealing face that must be re-machined flat |
| Machine tool beds, guideways and slides | Wear surfaces that are ground or scraped after welding — hardness variation shows up immediately |
| Gear housings, bearing pedestals, pump and valve bodies | Bearing bores and gasket faces that must be bored or faced back to tolerance |
| Casting defects — blowholes, shrinkage cavities, mis-runs | Excavated pockets in new castings, repaired before the part is released to the customer |
| Cracked or broken iron parts in maintenance | One-off repairs where no drawing exists and the part cannot be replaced |
| Cast iron joined to carbon or stainless steel | A dissimilar joint where a steel deposit would harden against the iron side |
Most ENi-CI failures reported by buyers trace back to technique rather than to the consumable. The alloy is forgiving of castings; it is not forgiving of high heat input. Five points carry most of the outcome:
Bake before use. Roughly 150 °C for one hour, and keep the electrodes in a holding oven or a sealed container until they go into the holder. A graphite-type coating that has absorbed moisture produces porosity that no amount of technique will remove.
Keep the current at the low end. Use the lowest current that still gives a stable arc. Excess current widens the dilution zone, and a wider dilution zone is a wider hard zone.
Stringer beads, not weaves. A common working rule is bead width no more than twice the core diameter and bead length no more than about ten times it. Short arc, fast travel, then let the part cool.
Peen each bead while it is still warm. Light, uniform hammering puts the deposit into compression and relieves the contraction stress that drives cracking. Skip this on the final finishing pass if the surface will be machined.
Clean slag between every pass. Cast iron repairs are usually short and numerous; trapped slag between them is the most common cause of a leak found at pressure test.
Preheat is a decision, not a rule. Thin sections and low-restraint repairs are commonly welded cold. Thick castings, long cracks and joints that cannot move should be brought to roughly 150–200 °C first. If the part is a pressure-containing or safety-related component, the procedure should be qualified and the decision recorded, not improvised at the bench.
| Diameter | Standard length | Current, flat | Current, vertical / overhead |
|---|---|---|---|
| 2.5 mm | 300 mm | 60–90 A | 50–80 A |
| 3.2 mm | 350 mm | 90–130 A | 80–110 A |
| 4.0 mm | 400 mm | 150–180 A | 120–150 A |
| 5.0 mm | 400 mm | 180–210 A | 150–190 A |
These are working ranges, not limits; the data sheet supplied with each batch takes precedence. Two selection notes from experience: thin walls and edge repairs go better on 2.5 mm at the low end of the range, because a small pool is easier to keep away from the edge than a large one is to control. And on a deep excavation, filling with 4.0 mm and finishing the top passes with 3.2 mm usually produces a flatter, more machinable surface than running one diameter throughout.
These three nickel-based electrodes are sold side by side and are frequently confused. The differences are not marketing; they change what the repair can carry and what it costs.
| Electrode | Deposit | Choose it when |
|---|---|---|
| ENi-CI (Z308 / EZNi-1) | Ni 90%+, soft austenitic | Machinability and crack resistance matter more than strength — thin sections, finished surfaces, visible castings |
| ENiFe-CI (Z408) | Ni ≈45–60%, balance iron | Thicker sections, higher tensile strength required, larger repair volume — lower cost per kilo and less sensitive to dilution |
| ENiCu-B (Z508) | Ni-Cu, Monel type | Cast iron to steel or to copper alloys, and repairs where a closer thermal expansion match to the iron is wanted |
An honest supplier tells you when to buy something else, and this is one of those cases:
Large-volume production welding of ductile iron. ENiFe-CI costs less and carries more load. Specifying pure nickel here spends money without gaining machinability the job does not need.
Structural castings under calculated load. A nickel deposit is ductile but not strong. If the joint is designed to a stress figure, the design should be reviewed before the electrode is chosen.
Castings that cannot take arc heat at all. Very thin or thermally sensitive parts are sometimes better brazed than welded. If your part falls into that category, say so in your enquiry — we supply silver brazing alloys and preforms as well, and we will tell you which route we would take.
Standard diameters are held in stock; cut length, pack quantity and label are made to order. Because a graphite-type coating is hygroscopic, packaging is part of the product, not an afterthought:
Moisture-barrier boxes with an inner liner, in 1 kg, 2 kg and 5 kg formats, or the pack weight your line actually consumes in a shift
Sealed tubes for small quantities and for site work, where an opened box would sit half-used for weeks
Custom cut length to match your fixture or your automated feed, so the stub end is a known quantity rather than a variable
Private-label cartons printed with your own brand, article number and barcode, for distributors and for OEM spares kits
Batch documents — deposit chemistry and mechanical properties against the classification, plus a certificate of conformity. Mill certificates and third-party test reports are available on request.
Every box carries the heat number, the classification and the baking recommendation. If a repair is later questioned, that label is the first thing anyone asks to see.
ENi-CI. The final two characters are the letters C and I, for cast iron. Catalogue pages very often print it as ENi-C1 with the digit one, or as ENiCl, and a few buyers search that way. All three refer to the same AWS A5.15 classification, and the electrode in the box is the same.
Yes — that is the reason most buyers choose it. A nickel deposit holds carbon in solution rather than forming hard carbides, so the weld and the boundary beside it stay cuttable with normal tooling.
Not always, and not never. Thin sections and free-to-move repairs are commonly welded without preheat. Thick castings, long cracks and restrained joints should be brought to roughly 150–200 °C. Section thickness and restraint decide it.
It is used on nodular irons where a machinable, ductile deposit is the priority. On thick ductile iron sections carrying load, ENiFe-CI is usually the better commercial and metallurgical choice.
Yes. It is a common choice for cast iron to carbon steel and cast iron to stainless joints, where a steel electrode would harden against the iron side of the interface.
Send the diameter, the cut length, the pack weight and the quantity, plus the casting grade if you know it. If you are still choosing between ENi-CI and ENiFe-CI, send the section thickness and the service conditions instead and we will quote both so the comparison is on paper.