Surface Treatment for Die-Cast Aluminum & Magnesium in Vietnam: Etching, Desmutting & Non-Phosphate Conversion

As giants like Samsung, LG, and Foxconn expand in Vietnam, the application of light metals (Die-Cast Aluminum & Magnesium) is exploding. From ultra-light laptop casings (Magnesium) to complex motorbike carburetors (Aluminum Die-cast), Vietnam’s manufacturing sector is upgrading its surface treatment requirements from simple “corrosion protection” to “high-end aesthetics” and “absolute eco-compliance.”

However, due to complex material compositions (high Silicon/Copper content), die-cast parts often suffer from smut, blackening, and poor coating adhesion during Die-Cast Aluminum & Magnesium pre-treatment. As a local chemical expert, Hongyi New Materials brings you deep Die-Cast Aluminum & Magnesium solutions tailored for these two challenging materials.

Aluminum Die-Casting Solutions: Creating a Uniform “Matte” Finish

Die-cast aluminum (e.g., ADC12) has high silicon content and often retains cold shuts, flow marks, and mold release agents. Traditional acid pickling often fails to remove these defects and can even cause over-corrosion.

Step 1: Leveling & Hiding Marks – LQ-A340 Aluminum Alkaline Etchant

To achieve a premium matte finish and hide die-casting imperfections, alkaline etching is the critical step.

• Unique Complexing Tech: LQ-A340 contains special long-life complexing agents. It dissolves microscopic peaks on the aluminum surface in a high-alkaline environment, creating a uniform satin finish that effectively masks minor mold marks and scratches.

• Scale Inhibition: Traditional etching often creates thick rock-like scale (Sodium Aluminate) on tank walls. LQ-A340 includes scale inhibitors, drastically reducing sludge buildup and lowering maintenance downtime costs.

Step 2: Smut Removal & Brightening – LQ-A434 Aluminum Bleaching Agent (Desmutting)

After etching, impurities like silicon, copper, and iron remain exposed on the surface, forming a loose black smut. If not removed, subsequent passivation or painting will fail 100%.

• Powerful Desmutting: LQ-A434 is designed for high-silicon alloys. Avoiding highly toxic Chromic acid or Hydrofluoric acid, uses a unique redox formula to instantly strip and dissolve stubborn “black smut.”

• Restoring Silver-White Luster: The treated surface reveals a clean, bright natural metal color, providing a perfect active base for subsequent Trivalent Chromium passivation or Chrome-free passivation.

Magnesium Alloy Solutions: Safe, Eco-friendly, Phosphate-Free Protection

Magnesium is the lightest structural metal but also the most reactive. In Vietnam’s humid air, bare magnesium oxidizes and turns black within hours. Furthermore, traditional treatments often involve Chromic Anhydride or High-Phosphate formulas, which are increasingly viable under Vietnam’s strict environmental regulations (MONRE).

Core Conversion – LQ-M533 Magnesium Alloy Phosphate-Free Coating Agent

This is a revolutionary eco-friendly product replacing traditional chromate treatments.

• Eco-Friendly & Phosphate-Free: Responding to green manufacturing, the formula is completely free of Phosphorus and Heavy Metals. Wastewater treatment is simplified, greatly reducing EHS (Environment, Health, Safety) pressure on factories.

• Superior Adhesion: LQ-M533 forms a dense organic-inorganic composite film on the magnesium surface. Although ultra-thin, this film acts like “Velcro,” firmly gripping subsequent paint or powder coatings, solving the chronic issue of paint peeling on magnesium.

Ultimate Protection – LQ-M600 Magnesium Sealing Agent

For magnesium parts used without painting, or those requiring extreme corrosion resistance, sealing is mandatory.

• Micropore Filling: Conversion coatings often have microscopic pores. LQ-M600 uses nanoparticles to penetrate and fill these voids, creating a hydrophobic barrier.

• Salt Spray Upgrade: Tests show that AZ91D magnesium treated with the “LQ-M533 Coating + LQ-M600 Sealing” combination easily surpasses 72-96 hours in Neutral Salt Spray (NSS) tests, meeting strict ocean freight export standards.

Why Do Vietnam’s FDI Factories Choose Hongyi Die-Cast Aluminum & Magnesium Agents?

1. Custom Process Development: There are many grades of Aluminum/Magnesium (5xxx, 6xxx, ADC12, AZ31, AZ91), each with different properties. Hongyi’s Haiphong lab can adjust chemical concentrations and process times based on your specific material to tailor an SOP for you.

2. Supply Chain Security: Magnesium production involves flammability risks, and chemical imports are strictly controlled. We maintain compliant stock in Northern Vietnam, ensuring you never face production stoppages due to chemical shortages.

3. Defect Analysis: Facing “blistering” or “black spots” on die-cast parts? Our engineers understand not just chemistry but also the die-casting process itself, helping you determine if the issue lies in pre-treatment or the casting substrate.

Frequently Asked Questions (FAQ)

Q1: Will LQ-A340 Alkaline Etchant significantly affect workpiece dimensions?

A: Etching is essentially chemical milling. LQ-A340 offers a stable and controllable reaction. We typically recommend an etching time of 30-90 seconds, which achieves the matte effect while keeping dimensional loss within microns, ensuring precision fits are not compromised.

Q2: How is the conductivity of Magnesium after LQ-M533 treatment?

A: The film formed by LQ-M533 is conductive (though resistance is slightly higher than bare metal). It is highly suitable for internal electronic structural parts requiring Electromagnetic Interference (EMI) shielding and grounding.

Q3: Does LQ-A434 Bleaching Agent contain Nitric Acid? Will it produce yellow fumes?

A: Our LQ-A434 utilizes fume-suppression technology. While it contains oxidizing acids, Nitrogen Oxide (yellow fume) volatility is extremely low at normal operating concentrations and temperatures, significantly improving the workshop environment.

Looking to Improve Your Yield Rate of Die-Cast Aluminum & Magnesium Surface Treatment?

Contact the Hongyi Engineering Team today for free samples and a bath analysis report.

• Zalo/ Hotline: 0827 626 966
• Address: Nhà Xưởng F.A3, lô CN3-03, Khu phi thuế quan và KCN Nam Đình Vũ (khu 1), thuộc Khu Kinh tế Đình Vũ – Cát Hải, Phường Đông Hải 2, Quận Hải An, Thành phố Hải Phòng, Việt Nam