We are Riddhi Siddhi Impex, a Mumbai-based Stainless Steel 904L shims manufacturer and supplier, established in 2002. We slit UNS N08904 super austenitic shims to ASTM A240 / ASME SA-240 in thicknesses of 0.03 mm to 5 mm. Our ISO 9001, 14001, and 45001-certified company keeps ready stock, carries a monthly supply capacity of 400-500 tonnes, and issues EN 10204 Type 3.1 / 3.2 mill test certificates on request.
Stainless Steel 904L shims are thin, flat spacers slit from a super austenitic grade built around 23 to 28% nickel, 19 to 23% chromium, 4 to 5% molybdenum, and a deliberate copper addition. Metallurgists developed 904L for dilute sulphuric acid duty, an environment that damages most stainless grades. Its pitting resistance number is about 35, so it withstands chlorides that would corrode 316L. Engineers use these spacers to set clearances and level mating faces in the acid-handling plant.
As a stainless steel 904L shims supplier and manufacturer, every shim leaves our slitting lines cut to the exact width a buyer specifies, from 3 mm to 2000 mm. Material ships in annealed soft condition to ASTM A240, with BA, 2B, or Matte surfaces and a choice of four edge conditions. Our quality system tracks each Stainless steel coil stock to dispatch.
We provide ASTM A240 904L shims in annealed condition only, with three surface finishes, four edge options, and cold rolled routes.
| Parameter | Details |
|---|---|
| Standard | ASTM A240 / ASME SA-240 |
| Thickness | 0.03 mm to 5 mm |
| Width | 3 mm to 2000 mm |
| Width Tolerance | ±0.1 mm |
| Condition | Annealed (Soft) |
| Surface Finish | BA (Bright Annealed), 2B, Matte |
| Supply Forms | Cold rolled (CR) |
| Edge | Slit edge, Mill edge, Deburred edge, Round edge |
Copper defines this grade. UNS N08904 shims pair 1.0 to 2.0% copper with a high nickel base, and that combination stays passive in reducing acids, above all, sulphuric, which strips the oxide film from ordinary austenitics. Carbon held at 0.020% max protects weld zones.
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.020 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | 0.035 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 19.0 - 23.0 |
| Nickel (Ni) | 23.0 - 28.0 |
| Molybdenum (Mo) | 4.0 - 5.0 |
| Copper (Cu) | 1.0 - 2.0 |
| Nitrogen (N) | 0.10 max |
Annealed SA 904L shims combine 490 MPa minimum tensile strength with 35% elongation, so thin gauges bend and form without cracking. The grade takes no hardening heat treatment; we supply it solution annealed only. Figures for very thin shim stock are indicative and vary with thickness.
| Property | Value |
|---|---|
|
Tensile Strength, minimum
|
490 MPa (71 ksi) |
|
Yield Strength (0.2% offset), minimum
|
220 MPa (31 ksi) |
|
Elongation in 50 mm, minimum
|
35% |
|
Hardness, maximum
|
90 HRB |
Buyers ordering against a regional specification can match our AISI 904L shims to the designations below. Each one names the same 25Ni-4.5Mo-Cu super austenitic stainless steel.
| Country / Standard | Designation |
|---|---|
| USA (UNS) | N08904 |
| Europe (EN) | X1NiCrMoCu25-20-5 |
| Germany (W.Nr) | 1.4539 |
| Japan (JIS) | SUS890L |
| Sweden (SS) | 2562 |
These 4 industries utilise the UNS N08904 shims we slit. All of them choose the grade for acid and chloride resistance first, and its strength.
Sulphuric acid plants are where 904L earned its reputation. Maintenance crews fit these shims beneath pump baseplates, reactor flanges, and heat exchanger saddles in acid concentrations that pit 316L within a season. The copper addition keeps the alloy passive in dilute sulphuric service, so shimmed joints stay tight between turnarounds.
Process skids in pharma and food plants go through aggressive clean-in-place chemicals daily. 904L shims in level mixers, filling heads, and vessel supports without shedding corrosion products into the product stream. Low carbon and a stable austenitic structure keep the material inert through repeated caustic and chloride wash cycles.
Refineries and gas plants run alkylation, amine, and produced-water circuits loaded with chlorides and acids. Alloy 904L shims align valve actuators, compressor skids, and instrument mounts in these units. Resistance to chloride stress corrosion cracking matters here because a cracked spacer under load throws a whole assembly out of line.
Bleach plants generate chlorine dioxide, hypochlorite, and hot acidic filtrates. 904L shimstock packs washers, bleaching towers, and digester fittings through stages where 316 needs replacing at every shutdown. Mills keep the grade on approved lists because it survives without the cost jump to a full 6Mo alloy.
Orders leave from our Mumbai and Taloja warehouses in wooden cases or on pallets, sea-ready.
| Parameter | Details |
|---|---|
| Packaging | Wooden cases, pallet packing |
| Incoterms | FOB, CIF, CFR, EXW |
| Dispatch Points | Mumbai and Taloja warehouses |
| Port | Mumbai |
| Standard Lead Time | 4 to 5 days |
| Urgent Dispatch | 2 to 3 days |
| Payment Terms | Advance, credit, LC |
| Certification | EN 10204 Type 3.1 / 3.2 on request |
Stainless Steel 904L shims price in India is around ₹300-₹450 per kg. Export buyers can expect $6.5-$10.5 per kg. Rates track nickel, molybdenum, and copper markets, while thickness, width, finish, and quantity move the final figure. Volume discounts apply to bulk orders, so call or WhatsApp us for today's rate.
We slit Stainless Steel 904L shims from 0.03 mm to 5 mm thick, in any width from 3 mm to 2000 mm at ±0.1 mm tolerance. Thinner material falls under our SS 904L foil range.
Stainless Steel 904L shims are not magnetic. The grade stays fully austenitic due to its 23 to 28% nickel content, and it remains essentially non-magnetic even after cold rolling.
SS904L shims resist sulphuric acid far better than 316L shims. They carry roughly double the nickel, more molybdenum, and a copper addition that 316L lacks, which is why acid plants pay the premium.
You can source Stainless Steel 904L shims in India from us at Riddhi Siddhi Impex. Our Mumbai warehouse holds N08904 shim stock for immediate dispatch, and we export worldwide as a supplier, stockist, and dealer. Phone or WhatsApp us and we will provide a quote within 24 hours.
