---
title: "Services and Process Capability | Black Cathodic E-Coating | Xintai Metal Surface Treatment Co., Ltd."
description: "Black cathodic e-coating (CED/AED) for small metal parts: six substrate families, 15–25 μm film, salt spray 1,000+ h on stainless and aluminum, insulation ≥ 10 MΩ at 500 V."
url: https://www.xted.site/en/services.md
canonical: https://www.xted.site/en/services.html
source: https://www.xted.site/en/services.html
format: markdown-mirror
note: >-
  This file is the Markdown mirror of https://www.xted.site/en/services.html, provided so AI crawlers and retrieval systems can read the body text at low cost. The page that canonical points to is authoritative; this mirror may lag behind it.
---
# Services & Process

Electrocoating (CED/AED) for small metal parts across six substrate families, holding 15–25 μm film, salt spray 1,000+ h on stainless steel and aluminum, and insulation resistance ≥ 10 MΩ at 500 V DC.

## What is black cathodic electrocoating (CED)?

Cathodic electrophoretic deposition (CED) is a waterborne coating process. The part is made the **cathode** and immersed in a positively charged waterborne e-coat bath. Current drives paint particles onto the surface, where they deposit as a uniform, dense film that is then baked and cross-linked.

Because deposition follows the electric field, internal cavities, crevices and edges that spray coating struggles to reach still receive a coating of consistent thickness. That is the core advantage of e-coating over paint or powder.

#### Black cathodic e-coat vs other black finishes

| Process | Typical film | Salt spray | Coverage | Best suited to |
| --- | --- | --- | --- | --- |
| **Black cathodic e-coat (CED)** | 15–25 μm | ≥ 1,000 h (stainless steel / aluminum) | Excellent (full coverage in blind spots) | Precision hardware, MIM parts, complex cavities — where appearance consistency and high corrosion resistance are both required |
| Black oxide / chemical conversion | 1–2 μm | Weaker (needs an oil dip) | Excellent | Ordinary structural parts with modest corrosion requirements |
| Paint / spray coating | 20–40 μm | Moderate | Fair (misses and sags are common) | Large or flat parts where appearance matters but the geometry is simple |
| Anodizing (aluminum) | 5–20 μm | Moderate | Excellent | Aluminum parts that need coloring or hard anodizing |
| PVD vacuum coating | 0.3–3 μm | Moderate | Fair (directional) | Highly decorative visible parts, at a higher cost |

Note: the table reflects general industry levels. Actual figures depend on substrate, pretreatment and paint formulation — the measured report governs.

## Substrates we can coat

We develop, run and supply coating processes for iron, stainless steel, aluminum, aluminum alloy, titanium alloy, magnesium alloy and MIM parts.

| Substrate | Typical incoming form | Process focus | Typical parts |
| --- | --- | --- | --- |
| **Iron-based** | Silicon steel, galvanized and cold-rolled steel stampings | Degreasing and phosphating quality come first; a uniform phosphate film is the foundation of salt spray resistance | Motor cores, EMI shields, brackets, spring contacts |
| **Stainless steel** | Stampings, CNC parts, etched parts | The passive film is dense, so a dedicated conditioning step is needed to secure adhesion | SIM trays, decorative plates, knife fittings, springs |
| **Aluminum / aluminum alloy** | Die-cast, extruded and CNC-machined aluminum | Die castings need attention to gas porosity and mold release residue; pretreatment cleaning must be stronger | Heat sinks, housings, gimbal brackets, speaker grilles |
| **Titanium alloy** | CNC parts, MIM parts | The oxide film is stable, so a titanium-specific activation is required | Wearable structures, premium decorative parts |
| **Magnesium alloy** | Die castings, extrusions | Chemically reactive with a narrow pretreatment window; parameters must be tightly controlled | Lightweight structures, laptop housings |
| **MIM parts** | Metal injection molded and sintered parts | Sintered surfaces are porous, so cleaning and sealing must be reinforced to avoid film defects | Hinge shafts, hinges, SIM trays, precision structures |

**Note:**our customers' upstream operations are concentrated in **stamping, die casting, CNC machining and MIM sintering** — four process families. If you are not sure whether your part suits e-coating, send us a drawing or a sample and we will assess it.

## Core process parameters

Typical ranges our standard black cathodic e-coat process holds. Your drawing and the measured report govern in every case.

| Coating thickness | **15–25 μm**(adjustable to your drawing; tolerance normally held within ±3 μm) |
| --- | --- |
| Salt spray (NSS) | **≥ 1,000 h on stainless steel and aluminum; ≥ 48 h on laminated silicon-steel cores**(varies with substrate and pretreatment) |
| Insulation resistance | **≥ 10 MΩ (measured at 500 V DC)**(for electrical and electronic parts that need insulation) |
| Film hardness | ≥ 2H (pencil hardness, GB/T 6739) |
| Adhesion | Class 0 (cross-cut, GB/T 9286) |
| Appearance | Matte black, gloss black, semi-gloss black (gloss adjustable on request) |
| Gloss level | Matched to your master plaque and measured on a ZGM gloss meter from Switzerland |
| Color difference | Batch-to-batch ΔE held under control, measured on a Konica Minolta spectrophotometer from Japan |
| Impact resistance | Meets the demands of normal hardware assembly and shipping |
| Environmental profile | Waterborne paint, low VOC, compliant with RoHS and similar requirements |

Note: the ranges above describe standard capability. For special requirements — higher salt spray, a specific color, a particular insulation class — we adjust formulation and process at sample stage and confirm feasibility with measured data. The instruments behind these figures are listed under [inspection & testing equipment](equipment.html#lab-equipment).

## The eight standard steps of black cathodic e-coating

Every step affects the final film. Key parameters are checked at fixed intervals and logged.

1

Racking

Racking chosen to suit the part: good contact for current, free drainage

2

Degreasing

Removes oil, fingerprints and machining fluid residue

3

Rinsing

Multi-stage rinsing with conductivity control to keep contaminants out

4

Conditioning / phosphating

Builds the conversion coating that adhesion and salt spray resistance depend on

5

Cathodic electrocoating

Voltage, bath temperature, solids content and pH under control

6

Ultrafiltrate rinse

Recovers drag-out paint and raises paint utilization

7

Baking and curing

Cured along a zoned temperature profile to cross-link the film

8

Final inspection

Sampled for coating thickness, ΔE, gloss and adhesion

#### Bath parameters we control

- **Solids content**: drives film thickness and throwing power; tested at fixed intervals and replenished
- **pH**: affects bath stability and film appearance; held inside the process window
- **Bath temperature**: affects deposition rate and thickness uniformity; temperature-controlled
- **Conductivity**: high rinse-water conductivity after pretreatment drags contaminants in; checked daily
- **Voltage and dwell time**: sets film thickness directly; fixed per part type

## How you can work with us

### Coating on customer parts

You send the parts; we coat and inspect them. This is how most work runs, and it suits customers who already stamp, die cast, machine or sinter in-house.

- Low-volume sampling supported
- High-volume production supported
- Packaging to your specification

### Free sample coating

Standard parts are sampled free of charge. Send a drawing or a sample and we return a process proposal; the sample run comes with measured data.

- 3–5 working days turnaround
- Measured film thickness, ΔE and more
- Several options to compare

### Process development

For a new substrate, a new look or an unusual performance target — very high salt spray, high insulation — we develop formulation and process parameters to order.

- Substrate compatibility trials
- Custom appearance
- Targeted performance tuning

## Process questions

### How thick can an e-coat film be?

Standard black cathodic e-coat is held at **15–25 μm**, a range that balances appearance, corrosion resistance and cost. Too thin and salt spray suffers; too thick and you risk sags, orange peel or interference with assembly tolerances. If you need something outside that range, we adjust voltage and dwell time at sample stage and verify the result.

### How is 1,000 hours of salt spray actually achieved?

Salt spray resistance comes down to three things:

1. **Pretreatment quality**: a dense, uniform phosphate film is the foundation; we test at fixed intervals and control the bath parameters
2. **The e-coat formulation**: a high-corrosion-resistant paint that gives the film its barrier performance
3. **Degree of cure**: full cure along a zoned profile, so the cross-linked structure is complete

The final word is a salt spray report from a third party or from your own laboratory; we supply the measured data either way.

### Does e-coating affect assembly dimensions?

Yes. A 15–25 μm film adds roughly that much per surface. For parts with a precision fit — hinge shafts, hinges, sliding components — we recommend that you **allow for the coating thickness on the drawing**, or state explicitly that critical dimensions are post-coat dimensions. We confirm fit tolerances with you at sample stage so the problem never reaches volume production.

### Will the racking contact points leave marks?

The part has to conduct current, so where the rack touches it there is **no coating at the contact point**, and a mark remains. There are two ways to handle it: agree the contact points at drawing stage and place them on non-visible surfaces, or touch in the marks afterwards (which adds operations and cost). We settle the racking plan with you at sample stage.

### Matte black or gloss black — what is the difference, and which should I choose?

Film performance is essentially the same; the difference is **surface gloss**:

- **Matte black**: low gloss, a fine and understated texture that hides fingerprints and scratches; mostly used for internal structures in consumer electronics and parts around optical components
- **Gloss black**: high gloss, a full and striking finish; mostly used for visible decorative parts
- **Semi-gloss black**: sits between the two

Whichever you choose, we match gloss to your master plaque on a ZGM gloss meter from Switzerland.

## Need to know whether your part suits e-coating?

Send a sample or a drawing and we will come back with a process proposal and measured data. Standard parts qualify for free sample coating.

[Request a sample run](contact.html)