Trivalent Chromium Passivation Solution | HW961 Series | Cr3+ Coating | RoHS Compliant
- Model
- HW-961-1
Review
Description
What Is Trivalent Chromium Passivation? (Cr³⁺ Explained)
What This Product Is
Trivalent chromium passivation is a chemical conversion coating process that deposits a thin, protective film of chromium(III) compounds onto zinc or zinc-alloy electroplated surfaces. Unlike traditional hexavalent chromium (Cr⁶⁺) treatments — which are toxic, carcinogenic, and now banned under EU RoHS and ELV directives — trivalent chromium (Cr³⁺) passivation delivers equivalent or superior corrosion resistance with minimal environmental and health risk.
The HW961 product series represents a next-generation Cr³⁺ passivation solution engineered for industrial precision: consistent film formation, tight pH control, and multi-standard performance including NSS 96h salt spray resistance, high-temperature stability, and chemical resistance to acids, alkalis, and solvents.
Physicochemical Properties — HW961 Series
| Parameter | HW961-1 (Self-Lubricating) | HW961-2 (Standard) |
| Appearance | Green to dark green solution | Green to dark green solution |
| pH Value | 14 ± 1 | 15 ± 1 |
| Solid Content (%) | < 2 | |
Density | 1.10 ± 0.10 g/cm³ | |
Cr³⁺ Content | 30–50 mg/m² | |
PMT Temperature | 80–120 °C | |
Environmental Compliance | EU RoHS Directive Compliant | |
Storage Temperature | 0–40 °C | |
Shelf Life | 6 months | |
Trivalent vs Hexavalent Chromium — Full Technical Comparison
One of the most-searched questions in the surface finishing industry is: how does trivalent chromium passivation compare to hexavalent chromium? The table below answers this directly, covering toxicity, regulatory compliance, corrosion performance, friction control, and waste treatment.
| Comparison Criteria | Trivalent Chromium (Cr³⁺) -- HW961 | Hexavalent Chromium (Cr⁶⁺) -- Legacy |
| Toxicity | Low — safe for operators and environment | High — carcinogenic, regulated/banned in EU/US |
| RoHS / ELV Compliance | Fully compliant | Non-compliant (prohibited) |
| Corrosion Resistance (NSS) | Up to 96h+ | 96–120h (conventional) |
High Temperature Stability | Excellent (240°C × 20 min, ΔE ≤ 3) | Moderate — degrades above 200°C |
Friction Control (Lubricated) | < 0.15 (ZY961-1) | Not available as standard |
Waste Treatment Costs | Low — simple treatment | High — Cr⁶⁺ reduction required before disposal |
Market Trend | Growing — industry standard | Declining — regulatory phase-out globally |
Why is trivalent chromium replacing hexavalent chromium? Hexavalent chromium (Cr⁶⁺) is classified as a human carcinogen (Group 1, IARC) and is restricted or banned under EU RoHS Directive 2011/65/EU, the ELV Directive 2000/53/EC, and REACH Regulation (EC) No. 1907/2006. Trivalent chromium (Cr³⁺) passivation achieves comparable corrosion resistance — typically NSS 48–96+ hours — without the toxicity, waste treatment costs, or regulatory exposure of Cr⁶⁺. The HW961 series is the direct drop-in solution for manufacturers transitioning to Cr³⁺. | ||
Product Performance — HW961-1 (Self-Lubricating Trivalent Chromium Passivation)
| SN | Test Item | est Conditions | Performance Standard |
| 1 | Corrosion Resistance | Flat surface NSS 96h salt spray test | White rust area ≤ 5% |
| 2 | High Temperature Resistance | 240°C × 20 min | Color difference ΔE ≤ 3 |
| 3 | Heat & Humidity Resistance | Open 50°C × 95% RH × 120h | Color difference ΔE ≤ 3 |
4 | Solvent Resistance | 80% alcohol, 50-cycle wipe test | Color difference ΔE ≤ 3 |
5 | Fingerprint Resistance | Vaseline coating for 1 hour | Color difference ΔE ≤ 3 |
6 | Artificial Sweat Resistance | 500ml H₂O + 500ml methanol, 7g NaCl, 1g urea, 4g lactic acid; 20s immersion | Color difference ΔE ≤ 3 |
7 | Alkali Resistance | 40°C, pH 10.5–12.5 alkaline solution, 2 min soak or spray | Color difference ΔE ≤ 3 |
8 | Acid Resistance | 40°C, pH 3.0–4.0 acid solution, 2 min soak or spray | Color difference ΔE ≤ 3 |
9 | Dyne Pen Test | Surface wettability check | ≥ 38# Dyne pen, no shrinkage |
10 | Kinetic Friction Coefficient | Dynamic friction measurement | < 0.15 (self-lubricating advantage) |
Product Performance — HW961-2 (Standard Trivalent Chromium Passivation)
HW961-2 delivers the full corrosion and environmental resistance profile of the HW961 series without the lubrication additive, making it a versatile choice for general industrial zinc-plated components including brackets, housings, hardware, and electrical connectors.
| SN | Test Item | est Conditions | Performance Standard |
| 1 | Corrosion Resistance | Flat surface NSS 96h salt spray test | White rust area ≤ 5% |
| 2 | High Temperature Resistance | 240°C × 20 min | Color difference ΔE ≤ 3 |
| 3 | Heat & Humidity Resistance | Open 50°C × 95% RH × 120h | Color difference ΔE ≤ 3 |
4 | Solvent Resistance | 80% alcohol, 50-cycle wipe test | Color difference ΔE ≤ 3 |
5 | Fingerprint Resistance | Vaseline coating for 1 hour | Color difference ΔE ≤ 3 |
6 | Artificial Sweat Resistance | 500ml H₂O + 500ml methanol, 7g NaCl, 1g urea, 4g lactic acid; 20s immersion | Color difference ΔE ≤ 3 |
7 | Alkali Resistance | 40°C, pH 10.5–12.5 alkaline solution, 2 min soak or spray | Color difference ΔE ≤ 3 |
8 | Acid Resistance | 40°C, pH 3.0–4.0 acid solution, 2 min soak or spray | Color difference ΔE ≤ 3 |
9 | Dyne Pen Test | Surface wettability check | ≥ 38# Dyne pen, no shrinkage |
Industry Applications & Use Cases
Automotive Industry
•Wheel bolts and lug nuts requiring precise torque-tension control (HW961-1)
•Engine fasteners, brackets, and suspension components exposed to high temperature and humidity
EV battery connector housings and structural parts requiring RoHS/ELV compliance
Electronics & Electrical
•PCB mounting hardware, terminal blocks, and connector shells
•Consumer electronics housings with fingerprint resistance requirements
Industrial control equipment requiring chemical resistance in factory environments
Industrial Manufacturing
•General-purpose zinc-plated fasteners for machinery and structural applications
•Surface treatment for zinc-alloy die-cast components
•Hardware for construction, HVAC, and white goods requiring durable corrosion protection
Regulatory / Compliance-Driven Transitions
•Drop-in replacement for hexavalent chromium processes to meet EU RoHS / ELV / REACH requirements
•Supplier qualification for Tier 1 automotive OEMs requiring IMDS-compliant surface treatment data
Frequently Asked Questions (FAQ) — Trivalent Chromium Passivation
The following questions and answers are structured to address the most common buyer and engineer queries in search engines and AI assistants. Each answer is factual, product-specific, and can be used directly as FAQ schema on your landing page.
What is trivalent chromium passivation and why does it replace hexavalent chromium?
Trivalent chromium (Cr³⁺) passivation forms a protective conversion coating on zinc-plated surfaces using only Cr³⁺ ions, eliminating toxic Cr⁶⁺. It is fully compliant with EU RoHS, ELV, and REACH regulations, and is now the global industry standard for environmentally safe metal surface treatment.
What is the difference between HW961-1 and HW961-2?
HW961-1 is a self-lubricating passivation solution with a dynamic friction coefficient < 0.15, ideal for threaded fasteners requiring torque-tension control. HW961-2 is a standard passivation formula offering the same corrosion protection without the lubrication additive, suited for general-purpose zinc-plated parts.
Which industries use trivalent chromium passivation solutions?
Key industries include: automotive (fasteners, brackets, connectors), electronics (PCB hardware, housings), aerospace, home appliances, construction hardware, and any sector requiring EU RoHS or ELV compliance for zinc-electroplated components.
What salt spray test (NSS) performance does HW961 pass?
Both HW961-1 and HW961-2 pass NSS 96-hour salt spray testing with flat-surface white rust area ≤ 5%, meeting or exceeding typical industry requirements for zinc passivation coatings.
Is HW961 compliant with EU RoHS and REACH regulations?
Yes. HW961 series contains no hexavalent chromium (Cr⁶⁺) and is fully compliant with the EU RoHS Directive and EU REACH framework. No restricted hazardous substances are used. Third-party test documentation is available upon request.
How does HW961-1 achieve low friction coefficient?
HW961-1 incorporates a proprietary self-lubricating additive into the passivation film. The result is a dynamic friction coefficient < 0.15, enabling predictable bolt clamp load in automotive assembly and reducing the risk of galling or thread stripping.
What is the storage temperature and shelf life of HW961?
HW961 solutions should be stored between 0–40°C and have a shelf life of 6 months from the date of manufacture when stored under recommended conditions. Keep containers tightly sealed and away from direct sunlight.
What substrate metals are compatible with HW961 passivation?
HW961 is primarily formulated for zinc-electroplated and zinc-alloy-plated steel substrates. For aluminum substrates or other base metals, please contact our technical team for compatibility evaluation.
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