- Phone
- *Title
- *Content
Sherardizing Service - Powder Zinc Diffusion Anti-Corrosion Coating for Steel Parts
| Share | |
|---|---|
| Categories | Galvanized Steel |
| Brand | MESCO Steel Wholesaler |
| Product Specifications | Sherardizing |
| Process | Powder sherardizing, solid-state zinc thermal diffusion |
| Coating Structure | Graded Zn-Fe intermetallic FeZn13 / FeZn7 layer |
| Coating Thickness | 20-120 um, set by temperature and dwell time |
| Surface Hardness | HV 200-400 |
| Service Life | 15-25 years at 20 um |
| Salt Spray Test | 1,080 h no red rust, GB/T 10123 |
| Bonding | Metallurgical, 300-350 MPa bond / 600-700 MPa adhesion, class 1 |
| Hydrogen Embrittlement | None, suitable for grade 10.9 and 12.9 fasteners |
| Base Materials | Carbon steel, alloy steel, cast iron, powder metallurgy parts |
| Thread Handling | Uniform coverage on threads and blind holes, no re-tapping |
| Standards | ASTM A1059, EN ISO 17668, EN 13811, BS 4921, ISO 14713-3, GB/T 35505-2017 |
| Applications | Fasteners, railway fittings, power towers, solar mounts, bridges, marine hardware |
| Download |  |
Sherardizing, also called powder zinc diffusion or thermal diffusion galvanizing, is a solid-state surface treatment. Steel parts are tumbling-heated in zinc powder inside a sealed rotating drum, zinc atoms diffuse into the steel surface and react with iron to form a graded Zn-Fe intermetallic layer. The coating is metallurgically bonded to the substrate, so it cannot peel, chip or flake the way an electroplated layer does.
MESCO supplies sherardizing as a contract treatment service for fasteners, railway components, power and solar hardware, bridge fittings and fabricated steel parts. Send us your drawings, base material and required coating class, and we return a process window, thickness range and quotation.
Fabricated steel parts before sherardizing treatment
How the Sherardized Layer Is Built
Solid-State Diffusion
Parts are loaded into a sealed drum with zinc powder and a filler. At 380-450 degC zinc vapor diffuses into the steel surface following Fick's laws, so coverage follows the geometry instead of the line of sight.
Intermetallic Reaction
Diffused zinc reacts with iron to form a graded structure: an outer FeZn13 layer, an intermediate FeZn7 layer and a diffusion zone bonded into the base metal. There is no sharp interface where a coating can detach.
Thickness by Time and Temperature
Layer depth is controlled by holding temperature and dwell time only, from 20 um up to 120 um, and it stays uniform on threads, inner walls, blind holes and recesses.
Measured Performance
| Property | Electro-galvanizing | Hot-dip galvanizing | Sherardizing |
|---|---|---|---|
| Service life at 20 um | 3-5 years | 5-20 years | 15-25 years |
| Surface hardness | HV 75-85 | HV 80-90 | HV 200-400 |
| Adhesion class | Class 4 | Class 3 | Class 1 |
| Coating thickness | 5-30 um | 5-100 um | 20-120 um |
| Hydrogen embrittlement risk | High | Moderate | None |
| Thread fit | Needs allowance | Zinc build-up on threads | Uniform, no re-tapping |
Salt spray reference tested to GB/T 10123: sherardized parts showed no red rust at 1,080 h, while hot-dip galvanized parts rusted at 96 h. Bond strength of the diffusion layer is 300-350 MPa with adhesion of 600-700 MPa, and the treatment raises fatigue strength and wear resistance of the base part instead of reducing them.
Why Buyers Switch to Sherardizing
Coating Does Not Peel
Metallurgical bonding means no plating interface. The layer survives bending, impact and press-fit assembly without flaking.
Safe for High-Strength Fasteners
No acid pickling and no electrolytic hydrogen, so 10.9 and 12.9 grade bolts carry zero hydrogen embrittlement risk.
Threads and Recesses Covered Evenly
Diffusion reaches inner walls and blind holes. Threaded parts keep their original fit class and need no post-machining.
Lower Life-Cycle Cost
A 20 um layer gives 15-25 years of protection, cutting re-galvanizing and replacement cycles on installed structures.
Clean Process
No molten zinc bath, no wastewater discharge and no acid fumes, which simplifies environmental permitting at the treatment site.
Standard-Compliant
Supplied to ASTM A1059, EN ISO 17668, EN 13811, BS 4921, ISO 14713-3 and GB/T 35505-2017.
Typical Parts We Sherardize
- High-strength bolts, nuts, washers, anchor bolts and threaded rod
- Railway fasteners, embedded parts, anti-falling beam devices and fish plates
- Highway guardrail hardware, bridge bearings and expansion joint parts
- Solar and wind mounting hardware, ground screws and pile brackets
- Ship fittings, offshore platform hardware and port equipment parts
- Mining machinery pins, chains, hydraulic fittings and wear parts
Ordering Information
| Base materials | Carbon steel, alloy steel, cast iron, powder metallurgy parts |
| Coating thickness | 20 um to 120 um, selected by service environment |
| Colour after treatment | Matte grey as-standard, passivation or topcoat on request |
| Part size limit | Set by drum and furnace dimensions, confirm per drawing |
| Inspection | Thickness by metallographic section, salt spray on request |
| Lead time and MOQ | Confirm with sales before order placement |
Frequently Asked Questions
Will sherardizing change the dimensions of threaded parts?
The diffusion layer grows inward and outward at a controlled rate. Because thickness is uniform and predictable, we reserve the allowance in advance so threads keep their fit class and need no re-tapping.
Can it be applied to hardened and high-strength steel?
Yes. The process runs without acid pickling and without electrolytic hydrogen, so there is no hydrogen embrittlement risk on high-strength fasteners of grade 10.9 and above.
How does it compare with hot-dip galvanizing on cost?
The unit treatment cost is higher than hot-dip, but a 20 um sherardized layer gives 15-25 years of service versus 5-20 years for hot-dip, which lowers total life-cycle cost on parts that are expensive to replace.
Which standard should I specify?
ASTM A1059 is the common choice for North America, EN ISO 17668 and EN 13811 for Europe, and GB/T 35505-2017 or JB/T 5067-1999 for domestic Chinese projects. We quote against any of them.
Send Your Parts for Sherardizing
Tell us the part type, base material, required thickness and quantity, and we will return a process proposal and quotation.
- 加载中···
Send us some details about your needs and feel free to ask any questionss. Our sales team will get back to you via email within a day.
- Phone
- *Title
- *Content