철강 산세용 HCl — 산업용 녹 제거 공정 및 기술 참고사항 (CAS 7647-01-0)

--- ## 1. 철강 산세(Pickling)란? 철강 산세는 냉간 압연, 용융 아연 도금, 정전 분체 도장 또는 금속 도금과 같은 후속 가공 단계 전에 탄소강 표면에서 산화철층(녹, 밀 스케일 및 열 잔류물)을 제거하는 화학 공정입니다. 이 공정은 대부분의 현대 철강 생산 라인 및 금속 가공 공장에 존재합니다. 열간 압연 또는 열처리 후 강철은 표면에 10-100 µm 두께의 산화 스케일 층을 형성합니다. 이 스케일은 3층 구조를 가집니다: 최외층은 Fe₂O₃(적철석 — 적갈색), 중간은 Fe₃O₄(자철석 — 검은색), 강철 기재에 인접한 층은 FeO(우스타이트 — 회색)입니다. 제거하지 않으면 산화층은: - 냉간 압연 시 표면 결함(피팅, 딤플링) 유발 - 강철 기재에 아연/페인트 코팅 접착 방해 - 페인트 아래 국부 부식으로 제품 수명 단축 HCl은 현재 철강 산업에서 가장 일반적인 산세제로, 전 세계 산세 시장의 약 70%를 차지하며, 빠른 반응 속도, 우수한 부산물 용해도 및 낮은 비용 덕분입니다. HCl의 CAS는 **7647-01-0**입니다. --- ## 2. Why Use HCl for Steel Pickling? Comparison with H₂SO₄ Although both HCl and H₂SO₄ can be used for steel pickling, HCl is preferred in most modern steel mills and processing workshops. The table below compares the two acids on key operational criteria: | Criteria | HCl (hydrochloric acid) | H₂SO₄ (sulfuric acid) | |---|---|---| | **Pickling speed** | Fast — 10-25 min at 25°C for carbon steel | Slow — needs heating to 50-80°C for equivalent speed | | **Operating temperature** | 20-40°C (room temperature — no heating needed) | 50-80°C (energy intensive heating) | | **By-product solubility** | FeCl₂/FeCl₃ fully soluble | FeSO₄ limited solubility, easily crystallizes | | **Steel base corrosion** | Yes — controlled by 0.1-0.5% inhibitor | Also present — harder to control at high temperature | | **Active surface creation** | Excellent — Cl⁻ effectively breaks down passive film | Medium — SO₄²⁻ less effective | | **Wastewater treatment** | Neutralize with NaOH → NaCl (less sludge) | Neutralize with NaOH/Ca(OH)₂ → Na₂SO₄/CaSO₄ (more sludge) | | **Evaporation** | HCl 32% slightly fuming, needs local exhaust | H₂SO₄ 98% almost non-volatile | | **Acid consumption/kg steel** | ~15-25 kg HCl 32%/ton steel | ~20-35 kg H₂SO₄ 98%/ton steel | | **Overall operating cost** | Lower — no heating + less sludge | Higher — energy + waste treatment costs | --- ## 3. 4-Step Steel Pickling Process ### Step 1: Degreasing - Solution: NaOH 5-10% or specialized alkaline degreaser (Loc Thien supplies NaOH 32%-50%) - Temperature: 60-80°C - Time: 5-15 minutes - Check: Surface must be "water break-free" ### Step 2: HCl pickling immersion | Parameter | Value | Notes | |---|---|---| | HCl concentration | 15-30% (diluted from HCl 32%) | Optimal ~18% | | Temperature | 25-40°C | No heating needed | | Immersion time | 10-30 minutes | Heavy-scale: 20-30 min; clean: 5-10 min | | Inhibitor | 0.1-0.5% vol | Reduces base corrosion up to 95% | | Fe content in bath | < 100 g/L | Above 100 g/L requires bath change | ### Step 3: Water rinsing - 2-3 counter-current rinse tanks - Final rinse pH ≥ 5.5 ### Step 4: Neutralization & drying - Quick dip through NaOH 1-2% - Dry with hot air at 80-120°C --- **Reference:** HCl 32%-35% handbook — choosing concentration, reading COA and legal compliance --- ## 7. Loc Thien Supplies HCl for Industrial Steel Pickling **Technical specifications — HCl 32%:** | Specification | Value | |---|---| | Formula | HCl | | CAS | 7647-01-0 | | Concentration | 32% ± 1% or 35% ± 1% | | Density (20°C) | 1.150-1.155 (32%) | | HS Code | 28061000 | | Packaging | 30L Carboys · 200L Drums · 1000L IBC · 5-30 ton tankers | **Why steel mills choose Loc Thien for HCl pickling?** - **Direct import, official channel** — COA and MSDS per batch, available for regulatory inspection - **6 warehouses nationwide:** HCMC, Dong Nai, BR-VT, Can Tho, Da Nang, Bac Ninh — delivery within 24 hours (Southern region) and 3-5 days (Northern and Central regions) - **5-30 ton tanker trucks** — suitable for all pickling bath scales - **Experience serving steel mills** — understands dilution concentration requirements, inhibitors and pickling safety procedures - **MST 0313650856** — established since 2016, framework contracts, full VAT invoices > 🛒 **Need HCl for steel pickling?** Hydrochloric Acid HCl 32%-35% — batch COA/MSDS, 5-30 ton tanker delivery nationwide. Hotline 0979 891 929. --- ## 8. FAQ **What is the optimal HCl concentration for carbon steel pickling?** 18% (diluted from HCl 32%) is the optimal concentration — balancing pickling speed (~3.0-3.5 g/m²/min) and base steel corrosion. **Does HCl pickling cause hydrogen embrittlement?** Yes — if not controlled. Solution: use inhibitor 0.1-0.5%, control immersion time, dry at 80-120°C after pickling. **Does HCl pickling corrode equipment?** Highly corrosive to stainless steel 304/316 — pickling baths: HDPE, PP, PVC or FRP composite. Pumps/valves: PVDF or polypropylene. **Where to buy HCl for steel pickling?** Loc Thien supplies directly imported HCl 32%-35% — batch COA/MSDS, 5-30 ton tanker delivery from 6 warehouses nationwide. Call 0979 891 929 for a quote within 15 minutes. --- **Loc Thien Investment Development Co., Ltd — MST 0313650856** · 452/6B Tinh Lo 10, P. Binh Tri Dong, HCMC · ☎ 0979 891 929 · hoachatlocthien.com