The questions customers ask most often about black cathodic electrocoating, grouped by company information, process technology, sampling and quoting, and how we work together.
The company specialises in metal surface treatment and heat treatment processing; its core business is black cathodic electrocoating (CED), covering matte black, gloss black and similar finishes for hardware parts made of iron, stainless steel, aluminium, aluminium alloy, titanium alloy and magnesium alloy. We also provide spray coating, coating equipment manufacturing and sales, and metal products development and sales.
The company is located at Room 501, Building 3, No. 252 Dalang Shuixin Road, Dalang Town, Dongguan, Guangdong, China, in Guangda Manufacturing · Dalang Tech Park, close to the Guanshen and Changhu Expressways and within one hour's drive of Shenzhen and Huizhou. Plant visits are welcome; please book by phone at least one working day in advance (181-2376-0267, Mr. Huang) so that we can arrange reception and a workshop tour route.
The plant covers 3,200 m², with a clean, well-organised workshop equipped with two automatic e-coat lines and two manual e-coat lines — four lines in total. The automatic lines handle stable, high-volume production, while the manual lines are used for sampling and pilot runs of small batches, multiple batches and irregularly shaped parts.
The company is certified to ISO 9001:2015 Quality Management System (certificate no. 38825Q01515R0S) and ISO 14001:2015 Environmental Management System (certificate no. 38826E00003R000); both certificates cover electrocoating. We also hold a Pollutant Discharge Permit (no. 91441900MAE2WKUY29001P, valid until 2030-09-01) and operate wastewater and waste-gas treatment facilities to specification, so production meets the required emission standards. The e-coat paint is water-based, contains no organic solvents and emits little VOC; an ultrafiltration system recovers drag-out paint, bringing paint utilisation above 90%. Scanned copies of the certificates and the official verification channels are on the Company Profile · Certifications page. If you need IATF 16949 or another specific system, mention it during project discussions and we will work with you on it.
We can coat iron-based substrates (stamped parts such as silicon steel sheet, galvanised sheet and cold-rolled sheet), die-cast and extruded aluminium, stainless steel, titanium alloy, magnesium alloy, as well as MIM (metal injection moulded) sintered parts — six substrate families in total. Each substrate gets a matched pretreatment sequence (degreasing, conditioning, phosphating, passivation) so that film adhesion and salt-spray performance stay consistent.
Standard black cathodic e-coat film thickness is held at 15–25 μm, with a tolerance of about ±3 μm. Too thin a film weakens salt-spray performance; too thick a film may sag, orange-peel or interfere with assembly tolerances. If you need a specific thickness, we can adjust voltage and time at the sampling stage to verify it.
In a neutral salt spray (NSS) test, stainless steel and aluminium alloy reach more than 1,000 hours, while laminated silicon steel cores reach about 48 hours, depending on the substrate and the pretreatment. Salt-spray resistance depends on three factors:
The measured salt-spray report is always the final word.
For electronic and electrical parts that require insulation, insulation resistance (at 500 V) reaches more than 10 MΩ. We test insulation resistance on insulating parts before mass production and keep the records.
| Process | Typical film thickness | Salt spray | Coverage uniformity |
|---|---|---|---|
| Black cathodic e-coat (CED) | 15–25 μm | ≥1,000 h (stainless steel / aluminium alloy) | Excellent (full coverage, even in recesses) |
| Blackening / oxidation | 1–2 μm | Weaker (requires oil dip) | Excellent |
| Paint / spray coating | 20–40 μm | Moderate | Fair (prone to misses and sagging) |
E-coat also uses more than 90% of the paint, against roughly 50% for spraying. For precision hardware that needs uniform film thickness, high salt-spray resistance and consistent appearance, black cathodic e-coating is the better choice.
Yes. A 15–25 μm film means that about 15–25 μm is added to each side. For parts with tight fit requirements (shafts, hinges, sliding parts), we recommend allowing for the e-coat film on the drawing, or stating explicitly that "critical dimensions are measured after coating". We can confirm fit tolerances at the sampling stage so that assembly problems do not surface in mass production.
Electrocoating requires the part to conduct current, so the contact points where the rack touches the part usually carry no paint film and do leave marks. There are two ways to deal with this: agree the contact positions at the drawing stage and place them on non-visible surfaces; or touch up the contact points afterwards, which adds process steps and cost. We confirm the racking plan with you at the sampling stage.
Film performance is essentially identical; the difference is in surface gloss:
We can match gloss to your standard panel using a ZGM gloss meter from Switzerland.
We check colour difference and gloss on every batch with a Konica Minolta colourimeter from Japan and a ZGM gloss meter from Switzerland, keeping a standard colour panel and batch records; we also spot-check film thickness with a Fischer coating thickness gauge from Germany. By managing quantified data we turn "looks about right" into a measurable standard, so that appearance stays consistent across batches.
Sintered MIM (metal injection moulded) parts have microscopic porosity, so direct e-coating tends to produce pinholes and craters, and cleaning liquid trapped in the pores can bleed out during baking and damage the film. There are three approaches:
In practice the three are usually combined, which is why MIM parts must be validated carefully at the sampling stage.
Die-cast aluminium problems come from three directions: porosity (gas escaping during baking causes pinholes), release agent residue (hurts adhesion), alloy segregation (uneven surface condition). Countermeasures include stronger degreasing and cleaning, an optimised baking ramp so that gas escapes slowly, and, where necessary, working with the die caster to improve the incoming surface condition.
Yes. The coating itself is non-magnetic, so it does not directly affect the magnet's magnetic performance, but it does add thickness (about 20–30 μm per side), and the effect of the coating on the assembly air gap must be considered in the magnetic circuit design. The baking temperature must also stay within what the magnet can tolerate; excessive temperature can cause irreversible magnetic loss. We confirm the magnet grade and temperature limits with you at the sampling stage.
Yes, but both need dedicated pretreatment:
These two substrates are relatively uncommon, so we recommend thorough validation at the sampling stage before scheduling mass production.
We offer free sampling for standard parts. Once you provide drawings or samples we issue a process plan, and sampling takes 3–5 working days after your parts arrive; the sample delivery includes measured data such as film thickness and colour difference. Special substrates, custom formulation development or dedicated racking may incur costs, and we will tell you clearly before sampling starts.
We support small-batch sampling; the exact MOQ depends on part size, substrate and process complexity. The plant runs two automatic and two manual e-coat lines, and the manual lines are dedicated to sampling and pilot runs of small batches, multiple batches and irregularly shaped parts, while the automatic lines handle stable high-volume production.
For an accurate quote, please provide:
The more complete the information, the more accurate the quote and process plan.
Yes. For items that need third-party reports, such as salt spray, insulation resistance and RoHS, we can submit samples for testing or work with a laboratory you nominate. Before mass production we recommend agreeing the test standard and acceptance criteria and writing them into the technical requirements.
Yes. We understand that drawings, processes and customer information are trade secrets for a hardware manufacturer, so we are willing to sign an NDA at the very start of discussions and to keep incoming samples and drawings confidential. The cases on this site are presented in de-identified form by industry and process type, which reflects that same commitment.
We can assess it. Whether a part is suitable for e-coating comes down to three points: whether it conducts electricity (e-coating needs a conductive part), whether it can withstand the baking temperature (typically 160–180 °C), whether it has areas that must not be coated. Send us drawings or samples and we will give you a clear assessment of suitability.