Aluminiumdruckgussteile werden häufig in der Automobilindustrie verwendet, Elektronik, und Hardwareindustrie, aber ihrer rauen Oberfläche mangelt es oft an Schutz, Dekoration, oder bestimmte Funktionen. Oberflächenbehandlung aus Aluminiumdruckguss löst dieses Problem durch systematische Prozesse – dennoch fällt es vielen Ingenieuren schwer, die richtige Methode auszuwählen. In diesem Artikel werden Kernprozesse aufgeschlüsselt, Vergleiche, und Auswahlstrategien, die Ihnen helfen, fundierte Entscheidungen zu treffen.
1. Why Is Pretreatment the Foundation of All Surface Treatments?
Pretreatment eliminates surface defects and contaminants, directly determining the quality of subsequent treatments. Skipping or rushing this step leads to coating peeling, uneven coloring, or poor corrosion resistance. Below is a detailed breakdown of key pretreatment steps:
| Pretreatment Step | Kernzweck | Gemeinsame Methoden | Schlüsselnotizen |
| Entfette | Remove grease, release agent residue | Solvent cleaning, alkaline degreasing, Ultraschallreinigung | Choose methods based on contamination level (Z.B., ultrasonic for heavy grease) |
| Oxide Film Removal | Eliminate natural thin oxide layer and slight surface metamorphism | Weak alkaline solution soaking | Avoid strong alkalis—they may etch the aluminum surface |
| Sanding/Descaling | Clear embedded mold sand or dirt from die casting | Manual sanding, mechanical sanding | Focus on areas with dense sand (Z.B., gate or overflow grooves) |
| Deburring/Polishing | Grate entfernen (at parting lines) und glatte Oberflächen | Manual polishing, mechanical grinding | Over-polishing closes pores (hurts coating adhesion); under-polishing leaves burr defects |
| Sandblasting/Shot Blasting | Improve surface roughness (boost coating adhesion) | Abrasive particle spraying (Alumina, Glasperlen) | Uniform spraying is critical—avoid uneven roughness |
Special Note for Porosity: Verwenden Imprägnierung (fill tiny pores with resin or wax) to improve air tightness—this is a must for subsequent dense treatments like electroplating.
2. Protective Treatments: Which One Fits Your Corrosion Resistance Needs?
Protective treatments extend the service life of die casting aluminum parts. Below is a comparison of the most common methods to help you choose:
| Treatment Type | Arbeitsprinzip | Vorteile | Einschränkungen | Ideale Anwendungsszenarien |
| Chemical Conversion Film | Chemical reaction forms a thin protective film (Z.B., Chromat, phosphate) | Niedrige Kosten, simple process; good pre-coating base | Poor long-term corrosion resistance | Short-term protection (Z.B., temporary storage) or pre-coating for spraying |
| Anodisierung | Electrochemical reaction generates a thick alumina film (hart, porös) | Hohe Härte (Tragenresistent); Hervorragende Korrosionsbeständigkeit | Die castings’ high porosity causes film blistering; poor dyeing effect | Parts needing high corrosion resistance (Z.B., Meereshardware, Outdoor -Vorrichtungen) |
| Elektroplierend | Electrolysis deposits metal layers (Chrom, Nickel) auf der Oberfläche | Dual benefits: Korrosionsbeständigkeit + Dekoration; hohe Härte (Chrombeschichtung) | Complex pretreatment; strict control of chemical solutions (to avoid pore defects) | Decorative-cum-protective parts (Z.B., Kfz -Trim, bathroom fixtures) |
| Sprühen | Apply coatings (Pulver, flüssig, electrophoretic) auf der Oberfläche | Rich colors; good coverage (fits complex shapes); powder coating is eco-friendly | High-temperature curing (needs temperature control to prevent deformation) | Teile mit komplexen Formen (Z.B., elektronische Gehäuse, Küchengeräte) |
3. Dekorativ & Functional Treatments: Meet Special Requirements
Beyond protection, decorative treatments boost product value, während functional treatments enable specific performance.
3.1 Decorative Treatments: From Matte to Metallic Shine
| Behandlung | Effect Description | Key Process | Einschränkungen | Target Products |
| Polished/Brushed | Glänzend (poliert) or textured (gebürstet: straight grain, studded grain) Oberfläche | Mechanisches Schleifen + Polieren | Requires high initial surface quality | High-grade hardware (Z.B., Wasserhahngriffe, luxury electronic casings) |
| Sandblasting Effect | Uniform matte surface | Fine abrasive spraying | Cannot hide major surface defects | Parts needing low-gloss appearance (Z.B., Industriekontrollpaneele) |
| Anodisierung + Färbung | Färberei (organic dyes) or electrolytic coloring (Bronze, Schwarz) after sulfuric acid anodizing | Anodizing → coloring → sealing | Die castings’ porosity limits dyeing uniformity | Semi-decorative parts (Z.B., medium-grade furniture hardware) |
| Vacuum Coating (PVD) | Deposits metal/ceramic films (Gold, rose gold, Titan) via physical vapor deposition | High-vacuum environment + ion sputtering | Requires highly smooth substrate surface | High-end decorative parts (Z.B., Smartphone -Rahmen, Luxus Uhrenfälle) |
3.2 Functional Treatments: Tailored to Performance Needs
| Functional Requirement | Behandlungsmethode | Anwendungsbeispiele |
| Leitfähigkeit | Electroplating copper/silver; conductive oxidation | Elektronische Anschlüsse, electromagnetic shielding parts |
| Isolierung | Anodisierung (dicker Film); polyurethane insulating paint coating | Motor components, electronic insulation brackets |
| Abriebfestigkeit | Hard anodizing (film thickness: 20-50μm); PVD durable film; wear-resistant spray coating | Bewegliche Teile (Z.B., Getriebe), Zylinder, pneumatic components |
4. 4 Key Factors to Choose the Right Surface Treatment Process
Choosing a process is not about “the best” but “the most suitable.” Consider these four factors:
- Final Requirements: Clarify priorities—Is it corrosion resistance (Z.B., outdoor parts need anodizing), Dekoration (Z.B., luxury parts need PVD), oder Funktionalität (Z.B., connectors need conductive plating)?
- Materialeigenschaften: Alloy composition and surface quality matter. Zum Beispiel, ADC12-Aluminiumlegierung (high silicon content) may affect electroplating uniformity; porous surfaces require impregnation first.
- Kosten & Umweltfreundlichkeit: Balance budget and regulations. Chrombeschichtung (hohe Kosten, giftig) is being replaced by eco-friendly options like powder coating or PVD.
- Produktionsmaßstab: Automatisierte Prozesse (Z.B., Elektrophorese, Pulverbeschichtung) suit mass production; manual polishing/PVD fits small-batch high-end products.
Yigu Technology’s Perspective on Die Casting Aluminum Surface Treatment
Bei Yigu Technology, Wir glauben pretreatment precision and process matching are the keys to successful die casting aluminum surface treatment. Im Laufe der Jahre, we’ve seen many projects fail due to neglected porosity (no impregnation) or mismatched treatments (Z.B., using anodizing for highly porous ADC12 parts). We advocate a “test-first” approach: conduct small-batch trials to verify pretreatment effectiveness and coating adhesion before mass production. Zusätzlich, as environmental regulations tighten, we prioritize eco-friendly processes like powder coating and chrome-free conversion films—helping clients meet both performance and sustainability goals.
FAQ (Häufig gestellte Fragen)
- Q: Why do die casting aluminum parts often have blistering during anodizing?
A: The main cause is high surface porosity of die castings. During anodizing, air or moisture in pores expands under electrolysis, leading to blistering. Solve this by adding an impregnation step before anodizing to seal pores.
- Q: Which is more cost-effective for mass-produced outdoor aluminum parts—anodizing or powder coating?
A: Powder coating is more cost-effective. It has lower equipment investment than anodizing, faster curing speed (geeignet für die Massenproduktion), and excellent outdoor weather resistance. Anodizing is better only if ultra-high hardness is required.
- Q: Can vacuum coating (PVD) be applied to die casting aluminum parts with rough surfaces?
A: NEIN. PVD requires a highly smooth substrate (Ra ≤ 0.2μm). Rough surfaces will cause uneven film deposition, sowohl das Aussehen als auch die Verschleißfestigkeit beeinträchtigen. Raue Teile zunächst durch Feinpolieren oder Sandstrahlen vorbehandeln, um die Oberfläche zu glätten.