Hangbo Alloy Group
Shanghai · Est. 2012
How nickel-alloy cladding and overlay welding protect reactors, valves and furnace parts from corrosion, with filler choices and procedure basics.
When a vessel or fitting must resist hot acid, chloride or sulfidation but the whole part cannot be made of solid nickel alloy, engineers clad the wetted surface with a corrosion-resistant overlay. A few millimetres of Inconel, Hastelloy or similar deposit on a carbon-steel shell gives the chemistry where it matters and keeps the cost down. This guide covers when to clad, which filler metals to specify, and what a sound procedure looks like.
Cladding pays off wherever the corrosion envelope is local — the inside of a reactor, a valve body bore, a transfer line elbow, or a tube sheet. Solid nickel alloy would work but is expensive and sometimes hard to source in thick section. An overlay of a few millimetres delivers the same surface chemistry. For sulfidation-prone refinery parts this is the standard economy move, described alongside sulfidation resistance of the parent grade.
The overlay chemistry should match the service. For general aqueous corrosion and chlorides, Inconel 625-type wires are common; for reducing acid, Hastelloy C-276-type deposits are preferred, and the choice between C-276 and C-22 is worth a look at the Hastelloy C-276 vs C-22 comparison. Where the base is large and the overlay thin, dilution from the substrate matters — procedures are written to keep iron pickup low so the first sound layer keeps its nickel-alloy properties. See the Hastelloy C-276 composition for the target chemistry.
Overlay is most often applied by submerged-arc or gas-metal-arc strip/cladding for large flat areas, and by weld overlay for complex bores. Key controls are interpass temperature, a verified dilution ratio, and ferrite management where relevant. Acceptance is by liquid-penetrant examination plus a chemistry check on the top layer; for critical sour service the procedure also meets the relevant sour-environment welding rule. Shanghai Hangbo Alloy Group supplies both the backing nickel alloys and the matching welding forms used in these overlays.
Two mistakes dominate field rejects: too much dilution, which drags the overlay toward the base metal's chemistry and loses corrosion resistance; and cracking from thermal mismatch on thick sections. Both are managed up front with a qualified procedure and a dilution sample, not found in service. Pairing the overlay with the right solid grade — for example reviewing carburization-resistant alloys for furnace parts — keeps the whole assembly coherent.
It depends on the service: Inconel 625-type overlays for chlorides and general corrosion, Hastelloy C-276 or C-22-type for reducing acids. The choice tracks the same logic as solid alloy selection, so compare grades such as in the C-276 vs C-22 guide.
Typically 3–6 mm of sound, low-dilution deposit, qualified so the top layer meets the target nickel-alloy chemistry. Thickness is set by the corrosion allowance of the service, not by a fixed rule.
Yes, when the overlay grade is a high-nickel alloy suited to sulfur-bearing heat — the same grades discussed under sulfidation of nickel alloys. It is the standard way to protect refinery furnace and reactor internals economically.
As a dedicated nickel alloy manufacturer serving chemical processing, oil & gas, power generation sectors, Hangbo Alloy Group supplies the grades discussed here across all standard product forms with full ASTM/ASME documentation and EN 10204 3.1 certification. Our material is specified for applications where corrosion resistance, high-temperature strength, and traceable quality are non-negotiable. See our production & testing facilities for more on how every heat is verified.