---
title: "Case Studies: Black E-Coating Applications | Xintai Metal Surface Treatment Co., Ltd."
description: "Six anonymised black e-coat cases from Xintai: MIM hinges, laminated motor cores, die-cast drone frames, NdFeB magnets, server shielding and titanium wearables."
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# Case Studies

The cases below are grouped by industry and process type. Customer names and part numbers are anonymised under NDA; only the process approach and the reasoning behind it are shown.

## Industries we serve

Our customers come from consumer electronics, automotive electronics, drones, AI hardware and cross-border hardware programmes, including several industry leaders and their tier-1 and tier-2 suppliers (names withheld under NDA).

### Consumer electronics

Black e-coat for MIM precision parts, stainless steel stampings and CNC-machined aluminum: typically folding-screen hinges, SIM trays, camera brackets and EMI shields.

MIM parts · Stainless steel · Matte black

### Automotive electronics

Motor cores, sensor housings and connector shells where salt spray resistance and electrical insulation are explicit requirements.

Silicon steel · SST≥48h · Insulation ≥ 10 MΩ

### Drones and smart devices

Gimbal brackets, airframe structures and folding hinges — lightweight metal parts where appearance consistency and weather resistance both matter.

Die-cast aluminum · Gloss black · Complex cavities

### AI hardware and servers

Heat sinks, chassis brackets and shielding parts that must stay insulating, corrosion resistant and dimensionally stable.

Aluminum alloy · Functional e-coat · Insulation

### Cross-border hardware OEMs

Black e-coating that meets export environmental requirements (RoHS, REACH) for brands selling across borders.

Export compliance · RoHS · REACH

### Supporting supply chain

We also coat for the tier-1 and tier-2 metalworking shops behind these customers — stamping, die casting, CNC machining and MIM sintering plants.

Stampings · Die castings · MIM sintered parts

Note: customer names are cited only to describe capability. Specific programmes, part numbers and volume data are bound by NDA; we can go into detail once one is signed.

## Case studies in detail

Each case covers the application, the process difficulty, our solution and the result actually achieved.

Case 01 · Consumer electronics, MIM

### Matte black e-coat on MIM hinges and SIM trays

| Application | MIM precision parts for folding phones and TWS earbuds need a matte black finish that matches the adjacent plastic parts. |
| --- | --- |
| Process challenge | ① MIM sintered surfaces are porous and prone to pinholes. ② Hinges are moving parts, so coating thickness affects assembly tolerance. ③ Multiple parts in one batch must match in color. |
| Our solution | Added ultrasonic cleaning and sealing to pretreatment; held coating thickness at 18–22 μm and validated assembly at sample stage; built a master color plaque with a spectrophotometer and compared every batch against it. |
| Result achieved | 18–22 μm coating; batch ΔE ≤ 1.0; matte gloss matched to the master plaque; assembly tolerance validated by the customer. |

Case 02 · Automotive electronics

### High-corrosion black e-coat for automotive motor cores

| Application | Motor cores and sensor housings that work long term in humid, salt-laden conditions and must also insulate electrically. |
| --- | --- |
| Process challenge | ① The gaps between laminations must be covered. ② Salt spray requirements are strict. ③ Insulation resistance must pass. |
| Our solution | Reworked the phosphating pretreatment for a denser conversion coating; selected a high-corrosion-resistant paint; used throwing power to reach the lamination gaps; tested insulation resistance batch by batch. |
| Result achieved | NSS ≥ 48 h on laminated silicon-steel cores; insulation resistance ≥ 10 MΩ at 500 V DC; adhesion class 0. |

Case 03 · Drones

### Gloss black e-coat on drone aluminum structures

| Application | Gimbal brackets and airframe aluminum parts are visible components: they need a gloss black look while keeping added weight low. |
| --- | --- |
| Process challenge | ① Gas porosity in die-cast aluminum causes pinholes during baking. ② Complex cavities and deep holes must be covered. ③ No sags or orange peel allowed on visible surfaces. |
| Our solution | Strengthened degreasing to remove mold release residue; tuned the bake ramp so gas escapes slowly; used throwing power to reach the cavities; matched gloss to a gloss black master plaque with a gloss meter. |
| Result achieved | Full coverage in complex cavities with no misses; uniform coating with no sags; gloss black matched to the master plaque. |

Case 04 · Magnetic materials

### Anti-corrosion black e-coat for NdFeB magnets

| Application | Sintered NdFeB magnets used in motors and acoustic devices oxidize easily and need a protective coating. |
| --- | --- |
| Process challenge | ① Porous magnet surfaces trap cleaning liquids. ② Too thick a coating closes the assembly air gap. ③ Bake temperature must not demagnetize the parts. |
| Our solution | Dedicated pretreatment and sealing; kept coating thickness in a workable window; confirmed the temperature limit for each magnet grade and adjusted the curing curve accordingly. |
| Result achieved | Continuous coating with no porosity; no loss of magnetic performance. |

Case 05 · AI hardware and servers

### Insulating e-coat for server shielding and brackets

| Application | Metal EMI shields and rail brackets inside AI servers must insulate and resist corrosion without interfering with insertion or assembly. |
| --- | --- |
| Process challenge | ① Insulation must pass consistently. ② Coating thickness must not affect rail and insertion tolerances. ③ Coating must not flake off and contaminate the airflow path. |
| Our solution | Applied a functional e-coat formulation; capped coating thickness tightly; verified adhesion to prevent flaking; sampled insulation resistance batch by batch. |
| Result achieved | Insulation resistance ≥ 10 MΩ at 500 V DC; adhesion class 0; dimensional tolerances met for assembly. |

Case 06 · Smart wearables

### Fine matte black e-coat on titanium wearable parts

| Application | Metal structures for smartwatches and smart glasses sit against the skin, so surface feel and sweat resistance both matter. |
| --- | --- |
| Process challenge | ① Titanium's stable oxide film makes adhesion hard to guarantee. ② The finish must be a fine matte. ③ It must resist sweat corrosion. |
| Our solution | Used a titanium-specific activation in pretreatment; a matte black formulation that hides fingerprints and fine scratches; matched gloss to the master plaque. |
| Result achieved | Adhesion class 0; consistent matte black gloss; passed sweat corrosion testing. |

## How we work together

Six steps from first conversation to volume delivery, each with a defined deliverable.

1

Requirement review

Substrate, dimensions, performance requirements and volume

2

Process assessment

Feasibility judgement and a preliminary process proposal

3

Free sample coating

Samples delivered in 3–5 working days for standard parts

4

Data confirmation

Measured coating thickness, ΔE and other data for sign-off

5

Quotation and volume

Quotation after approval, then production scheduling

6

Delivery and support

On-time delivery, batch records archived and traceable

## Common questions about working with us

### Why don't the cases show full customer names?

Most of our customers are under NDA, so we do not disclose programmes, part numbers or volume data without authorisation. Cases are presented by **industry + process type** in anonymised form, purely to describe process capability and how we solve problems. If you need more background on the customers we work with, we are glad to talk once an NDA is in place.

### Can we sign a non-disclosure agreement?

Yes. Drawings, processes and customer information at a metalworking company are trade secrets. We are willing to sign an NDA at the very first meeting and to keep incoming samples and drawings confidential.

### Is sample coating charged for new customers?

For standard parts we offer **free sample coating**. Special substrates, dedicated formulation development or custom racking may incur a charge, which we confirm with you before any work starts.

## Want the full process behind a similar part?

Tell us your part type and performance requirements and we will come back with process advice and a sample run.

[Request a quote](contact.html)