Selecting the right surface treatment protects custom metal parts from galvanic and atmospheric corrosion while meeting cosmetic and electrical conductivity requirements. Below is our engineering comparison for custom CNC machined, extruded, and stamped components.
| Finish Type | Compatible Substrate | Typical Film Thickness | Salt Spray (ASTM B117) | Best Engineering Application |
|---|---|---|---|---|
| 1. Ultrasonic Washing & Passivation | Aluminum, SS 304/316, Brass | 0 μm (Zero dimensional change) | Substrate dependent | Tight-tolerance internal parts, weldments, pre-assembly |
| 2. Anodizing (Type II Clear / Black) | Aluminum (6061 / 6063 / 7075) | 8 – 25 μm (0.3 – 1.0 mil) | 336 – 500+ hrs | Heatsinks, audio chassis, precision CNC housings (MIL-A-8625) |
| 3. Cathodic E-Coating (Electrophoresis) | Cold Rolled Steel (CRS), Aluminum | 15 – 35 μm (0.6 – 1.4 mils) | 500 – 1,000 hrs | Automotive amplifier/AVAS brackets, speaker baskets, recessed geometries |
| 4. Electrostatic Powder Coating | Steel, Aluminum, Stainless | 60 – 120 μm (2.4 – 4.7 mils) | 500 – 1,000+ hrs | Outdoor enclosures, custom RAL/Pantone colors, textured finishes |
Design Rule: Accounting for Coating Build-Up
Type II anodizing grows ~50% into the aluminum and ~50% outward, whereas E-coating (15–35 μm) and powder coating (60–120 μm) add full thickness to all surfaces. Specify on your drawing whether tolerances apply before coating or after coating. We provide silicone plug masking for M3–M12 tapped holes and H7 dowel bores.
Automotive Acoustic & Thermal Standards
Our cathodic epoxy/acrylic electrocoat (E-coat) lines are engineered for automotive acoustic brackets and frames—delivering uniform recess coverage, zero heavy metals, low VOCs, and verified cross-hatch adhesion per ASTM D3359 / ISO 2409.
Need Advice on Surface Treatment & Masking?
Send your part drawing to sean@suhangmetal.com for an engineering recommendation.
Contact Our Engineering Team