Case Study: HCl 32% Steel Pickling — 2x Speed, 40% Less Waste at Phu My Steel Plant
Table of contents
TL;DR: A steel plant in Phu My Industrial Park (Ba Ria — Vung Tau) switched from H₂SO₄ 25% to HCl 32% in its pickling line. Results: pickling time dropped from 30 minutes to 15 minutes, HCl consumption 20–30 kg/ton steel, waste sludge reduced 40% thanks to FeCl₂’s higher solubility vs FeSO₄. HCl 32% is supplied with a COA and MSDS for every batch.
Steel Pickling Overview: H₂SO₄ vs HCl
Pickling — removing mill scale with acid — is an essential step in cold-rolled steel, galvanized steel, and steel pipe production. Iron oxide layers (Fe₂O₃, Fe₃O₄) formed on steel surfaces after hot rolling must be removed before downstream processing, otherwise surface defects appear on the finished product.
The two most common acids for carbon steel pickling are H₂SO₄ (sulfuric acid) and HCl (hydrochloric acid). Each has different operating characteristics:
| Factor | H₂SO₄ (Traditional) | HCl 32% |
|---|---|---|
| Operating temperature | 50–60°C (requires heating) | 25–40°C (room temperature) |
| Pickling speed | Slow at room temperature | 2x faster at same temperature |
| By-product | FeSO₄ (low solubility, forms sludge) | FeCl₂ (high solubility, less sludge) |
| Base metal attack | Higher (prone to over-pickling) | Lower (less over-pickling) |
| Fume control | Not required (minimal fumes) | Ventilation needed (HCl fumes) |
| Sludge treatment | Sulfate sludge, large volume | Chloride sludge, smaller volume |
See HCl 32% technical specifications from Loc Thien for concentration and specific gravity data.
Real-World Case Study: Phu My Industrial Park Steel Plant
Background
A steel pipe and structural steel plant in Phu My Industrial Park (Ba Ria — Vung Tau) operates a batch pickling line with a 12 m³ pickling tank. Previously, they used H₂SO₄ 25% at 55–60°C because operators were “accustomed to H₂SO₄” and believed HCl would be too corrosive to equipment.
Problems
- Slow pickling speed: Each batch took 25–35 minutes depending on steel grade. With 40,000 tons annual output, the line was frequently bottlenecked — waiting for pickling to finish before downstream processes.
- High energy consumption: Maintaining H₂SO₄ tanks at 55–60°C consumed ~400 kWh/day for steam heating. Boiler fuel (FO oil) for pickling alone was a significant recurring monthly cost.
- Excessive waste sludge: FeSO₄ crystallized in H₂SO₄ solution at low concentrations, producing ~18 tons/month of sludge — requiring a licensed hazardous waste contractor every month.
- Over-pickling risk: H₂SO₄ aggressively attacked the steel base when FeSO₄ concentration in the tank was high, causing surface pitting and increased steel loss (nearly 1% mass per batch).
Solution: Switch to HCl 32%
After a 2-month survey — with consultation from Loc Thien’s QC team (technicians Phan Cam Thuy and Vo Thi Nhu Hoa) — the plant decided to convert to HCl 32%.
Technical adjustments:
- Pickling tank: The existing tank (acid-resistant brick lining, reinforced concrete body) was usable with HCl 32% after brick joint sealing. The steam heating pipe was replaced with PVC — since HCl pickling runs mainly at room temperature, only light heating is needed when accelerating.
- Ventilation system: Added 2 wall-mounted exhaust fans above the pickling tank, routing fumes through a 5% NaOH absorption tower to neutralize HCl vapor before release.
- Inhibitor: HCl pickling can cause over-pickling at high concentrations without an inhibitor. The plant uses a commercial inhibitor at 0.2% of acid mass — reducing base metal attack from 8% to under 2%.
- Operating concentration: HCl 32% diluted to 8–12% in the pickling tank (per ASTM B600 recommendations), maintaining maximum Fe concentration at 13 g/100 ml before solution replacement.
Results After 4 Months
| Metric | Before (H₂SO₄ 25%) | After (HCl 32%) | Change |
|---|---|---|---|
| Pickling time per batch | 25–35 min | 12–18 min | -50% |
| Acid consumption/ton steel | 40–50 kg H₂SO₄ 25% | 20–30 kg HCl 32% | — |
| Operating temperature | 55–60°C | 30–35°C (room temp + light heating in cold season) | -42% |
| Heating energy | ~400 kWh/day | ~30 kWh/day (winter only) | -92% |
| Waste sludge | ~18 tons/month (FeSO₄) | ~10.8 tons/month (FeCl₂) | -40% |
| Sludge treatment cost (index) | 100 | ~62 | -38% |
| Surface quality | Dull, occasional smut | Bright uniform, no smut | Improved |
Line capacity increased from 40,000 to ~55,000 tons/year without adding new pickling tanks — thanks to halved batch time.
Annual Cost Savings Analysis
| Item | H₂SO₄ (index = 100 per item) | HCl 32% (index) | Change vs H₂SO₄ |
|---|---|---|---|
| Acid purchase | 100 | 114 | +14% (HCl costs more) |
| Heating fuel | 100 | ~8 | -92% |
| Sludge treatment | 100 | 61 | -39% |
| Equipment maintenance | 100 (tank needed frequent repairs due to FeSO₄ scaling) | 53 | -47% |
| Total | 100 | 94 | -6%/year |
Although HCl 32% has a higher per-kg price than H₂SO₄, total operating costs are lower thanks to energy, sludge treatment, and maintenance savings.
Why HCl Pickling Is Faster and Produces Less Sludge
Reaction Speed
Pickling reactions with HCl proceed quickly even at room temperature:
- Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O
- Fe₃O₄ + 8HCl → 2FeCl₃ + FeCl₂ + 4H₂O
- Fe + 2HCl → FeCl₂ + H₂
With H₂SO₄, the reaction is much slower at room temperature — requiring heating to 50–60°C for equivalent speed. The mechanism: H⁺ ions in HCl have higher activity than in H₂SO₄ because hydrogen bonding in H₂SO₄ impedes dissociation.
Waste Sludge
FeSO₄ (the by-product of H₂SO₄ pickling) has sharply decreasing water solubility as H₂SO₄ concentration rises — crystallizing and settling as sludge. FeCl₂ is almost completely soluble in HCl solution at all pickling concentrations, extending acid bath life and reducing sludge output by approximately 40%.
According to the American Galvanizers Association, HCl pickling allows operation with Fe concentration up to 13 g/100 ml before solution replacement — while H₂SO₄ only tolerates 8 g/100 ml. This explains the lower solution replacement frequency and reduced sludge volume.
Converting from H₂SO₄ to HCl — What to Check
Based on experience from the Phu My case study and other plants, Loc Thien summarizes 5 factors to verify before conversion:
- Pickling tank material: Acid-resistant brick-lined tanks, PVC, FRP, or polypropylene are compatible with HCl 32%. Unlined carbon steel tanks — not suitable.
- Ventilation system: HCl produces fumes above 40°C and when the tank is aerated. Adequate exhaust fans (recommended 6–10x tank volume/hour) and an alkaline absorption tower are needed.
- Pickling inhibitor: Mandatory for HCl pickling at concentrations >8%. Inhibitor concentration 0.1–0.3% of acid mass, depending on steel grade and operating temperature.
- Wastewater treatment: Spent FeCl₂ solution from HCl pickling can be recovered to produce FeCl₃ (water treatment coagulant) via chlorine injection. Reduces waste treatment costs.
- Operator training: Pickling workers familiar with H₂SO₄ need training on HCl concentration control and ventilation system operation. Loc Thien provides technical documentation and on-site guidance.
Documentation Supplied with HCl 32% for Export Factories
Each batch of HCl 32% supplied by Loc Thien comes with a COA and MSDS, and documents can be provided on request for customer audits. Heavy metal content (Pb, As, Cd, Cr, Hg) in HCl is checked on the COA for each batch.
Batch documentation is especially significant for steel plants with galvanizing lines or export steel production, where end customers ask for records of incoming chemicals. If a brand requires ZDHC records, contact us to confirm the documents currently available for each product.
HCl 32% Technical Specifications Table
| Parameter | Value |
|---|---|
| Trade name | HCl 32% Acid |
| Chemical formula | HCl |
| CAS number | 7647-01-0 |
| UN number | 1789 |
| Concentration | 32% ± 1% (per batch COA) |
| Specific gravity (20°C) | 1.159 g/ml |
| Appearance | Liquid solution, colorless to pale yellow, slightly fuming |
| Boiling point | ~106°C |
| Vapor pressure (20°C) | ~14 mmHg |
| Packaging | 30L Jerry can / 200L Drum / 1000L IBC / Tanker 5–30 tons |
Pickling Cost Comparison: H₂SO₄ vs HCl 32%
| Cost Type | H₂SO₄ 25% | HCl 32% | Difference |
|---|---|---|---|
| Acid price/kg (reference) | Lower | ~20% higher | HCl more expensive |
| Heating cost/ton steel (index) | 100 | ~5 | HCl 95% cheaper |
| Sludge treatment cost/ton steel (index) | 100 | 60 | HCl 40% cheaper |
| Line productivity | 100% | ~150% | +50% |
| Total operating cost/ton steel | Baseline | 5–8% lower | HCl more economical |
Technical Support & B2B Procurement Hotline
Loc Thien Chemical specializes in direct manufacturing of FeCl₂ / FeCl₃ and direct industrial supply of basic chemicals (NaOH, HCl, H₂SO₄, PAC, NaOCl, H₂O₂, FeSO₄) with direct B2B pricing and dedicated 5–30-ton tanker delivery across Vietnam.
- Hotline / Zalo: +84 979 891 929
- Official Email: [email protected]
- Direct Manufacturer: Ferrous Chloride (FeCl₂ 30%) & Ferric Chloride (FeCl₃ 38–40%)
- Primary Supplier: NaOH 32%/45%/50%/99%, HCl 32%, H₂SO₄ 98%, PAC 30–31%, NaOCl 10–12%, H₂O₂ 35%/50%
- Compliance & Quality: FeCl₂ ZDHC MRSL v3.1 test report (Smart testing, 5 substance groups, TUV Rheinland Vietnam), ISO 9001:2015, Quatest 3, Full COA & GHS SDS
FAQ
Is HCl pickling more corrosive to equipment than H₂SO₄?
HCl storage and use requires acid-resistant materials (PVC, FRP, acid-resistant brick). With properly designed equipment, service life is comparable to H₂SO₄. Note: HCl fumes can corrode steel structures in the workshop without adequate ventilation.
How much HCl is needed per ton of steel?
20–30 kg of HCl 32% per ton of steel pickled, depending on steel grade and oxide level. Less than H₂SO₄ in terms of pure acid mass because HCl pickling is more efficient at lower concentrations.
Can HCl be regenerated from spent solution?
Yes. Pyrohydrolysis technology (spray roasting furnace) regenerates HCl from FeCl₂, common in large steel mills. Medium-sized plants can sell spent FeCl₂ solution to FeCl₃ producers.
Does HCl 32% pickling reduce hydrogen embrittlement?
HCl pickling reduces hydrogen embrittlement risk compared to H₂SO₄ because hydrogen evolution is slower and inhibitor control is better. According to IspatGuru research, hydrogen permeability into the steel base is significantly lower with HCl.
Where to buy HCl 32% for steel pickling?
Loc Thien supplies HCl 32% and 35% from 6 warehouses nationwide (Ba Ria – Vung Tau, Dong Nai, Binh Duong, Da Nang, Can Tho and Bac Ninh), delivered by a fleet of dedicated tanker trucks. Batch COA/MSDS provided. Hotline 0979 891 929 — quotation within 15 minutes.
🛒 Need HCl 32% for industrial pickling? Get a Quote for HCl 32%–35% — Batch COA/MSDS, delivered nationwide. Hotline 0979 891 929.
Hotline
Call 0979 891 929 (0979891929) — contact Phan Cam Thuy or Vo Thi Nhu Hoa (QC Department) for technical consultation on H₂SO₄ to HCl pickling conversion, plant infrastructure survey, and HCl 32% pricing. Loc Thien supplies bulk quantities for enterprises, delivery to industrial parks within 24–48 hours.