Conformal Coating Electronics Assembly MG Chemicals MG Chemicals 422B PCB Protection Silicone Conformal Coating

MG Chemicals 422B Silicone Modified Conformal Coating: Application Guide and When to Use It

Jul 13, 2026

Quick Answer

MG Chemicals 422B is a 1-part, acrylic-silicone hybrid conformal coating with UV fluorescent indicator. It cures to a durable, flexible, smooth film that provides moisture, humidity, and thermal protection for PCBs and electronic assemblies. 422B bridges the gap between acrylic and silicone coatings — it is easier to rework than pure silicone, more heat-resistant than pure acrylic, and includes a UV indicator for coverage inspection. Apply in 2–3 thin coats by brush, spray, or dip; tack-free in 30 minutes, full cure in 24 hours at room temperature. For high-reliability applications (IPC-A-610 Class 3), verify dry film thickness of 25–75 microns and inspect under 365nm UV light for complete coverage.

Applying MG Chemicals 422B silicone modified conformal coating to a PCB circuit board

MG Chemicals 422B Silicone Modified Conformal Coating is one of the most versatile conformal coatings in the MG Chemicals lineup. As an acrylic-silicone hybrid, it combines the easy application and reworkability of acrylic coatings with the higher temperature resistance and flexibility of silicone — making it a strong choice for electronics that need more protection than a standard acrylic coating provides, without the rework difficulty of a pure silicone coating.

What Makes 422B Different from Other Conformal Coatings?

422B sits between pure acrylic and pure silicone coatings in terms of performance and reworkability:

  • Available formats: MG Chemicals 422B is stocked in aerosol, 1L, 1-gallon, and 20L pail sizes at MTE Solutions
  • vs. Pure acrylic: 422B offers higher temperature resistance and better flexibility across thermal cycles — better suited for environments with temperature swings
  • vs. Pure silicone: 422B is significantly easier to rework — it can be removed with standard conformal coating strippers, unlike pure silicone which requires mechanical removal or specialized solvents
  • UV indicator: Contains a UV fluorescent dye that glows under 365nm UV light for fast, reliable coverage inspection
  • UL 94V-0 rated: Flame retardant, suitable for applications with flammability requirements

422B Performance Specifications

Property 422B Value
Chemistry Acrylic-silicone hybrid (1-part)
Cure type Solvent evaporation (air dry)
Tack-free time ~30 minutes at 25°C
Full cure time 24 hours at 25°C
Operating temperature –65°C to +130°C
Dry film thickness (IPC-A-610) 25–75 microns (1–3 mils)
UV indicator Yes — 365nm UV-A inspection
Flammability UL 94V-0
Reworkability Good — removable with conformal coating stripper

How to Apply MG Chemicals 422B

  1. Clean the board first — remove all flux residue, oils, and contamination with IPA. Allow to dry completely. Conformal coating will seal in contamination if applied to a dirty board.
  2. Mask keep-out areas — cover connectors, switches, test points, and heat sinks with masking tape or liquid masking compound before coating.
  3. Apply by brush, spray, or dip:
    • Aerosol: Hold 20–30cm (8–12 inches) from the board. Apply in smooth, overlapping passes.
    • Brush: Use a clean, lint-free brush. Apply in smooth strokes — avoid overworking the coating.
    • Dip: Immerse board slowly, withdraw at a controlled rate, allow excess to drain.
  4. Apply 2–3 thin coats — allow each coat to become tack-free (~30 minutes) before applying the next. Multiple thin coats provide better coverage than one thick coat.
  5. Full cure: Allow 24 hours at room temperature before exposing to moisture or returning to service.
  6. Inspect under UV: Use a 365nm UV lamp in a darkened area to verify complete, continuous coverage. Gaps and thin spots appear dark under UV.

When to Choose 422B vs. Other Coatings

  • Choose 422B when: You need better temperature resistance than a standard acrylic but want easier rework than pure silicone — ideal for industrial electronics, automotive accessories, and outdoor equipment
  • Choose pure acrylic when: Frequent rework is expected and temperature range is moderate (–65°C to +125°C)
  • Choose pure silicone when: Maximum temperature resistance (–65°C to +200°C) is required and rework is rare

Frequently Asked Questions About MG Chemicals 422B

What is the difference between MG Chemicals 422B and 422C?

MG Chemicals 422B is an acrylic-silicone hybrid conformal coating, while 422C is available in both acrylic and silicone formulations. The 422B hybrid offers a balance between the reworkability of acrylic and the temperature resistance of silicone, with an operating range of –65°C to +130°C. Pure silicone 422C extends to +200°C but is significantly harder to rework. For most industrial and commercial applications, 422B provides the best balance of performance and reworkability.

Can MG Chemicals 422B be removed for rework?

Yes — 422B can be removed with standard conformal coating strippers. It is significantly easier to rework than pure silicone coatings, which require mechanical removal or specialized silicone strippers. For localized rework, the coating can also be carefully removed with a scalpel or by spot application of stripper. Always test the stripper on a small area first to verify compatibility with board materials and components.

Does MG Chemicals 422B meet IPC-A-610 requirements?

MG Chemicals 422B can be applied to meet IPC-A-610 conformal coating requirements when applied to the correct dry film thickness (25–75 microns / 1–3 mils) with complete, continuous coverage verified by UV inspection. The UV indicator in 422B fluoresces under 365nm UV light, making coverage inspection straightforward. For Class 3 high-reliability applications, document your process including application method, number of coats, cure conditions, and UV inspection results.

What sizes does MG Chemicals 422B come in?

MTE Solutions carries MG Chemicals 422B in aerosol (340g/12oz), 1-liter can, 1-gallon can, and 20-liter pail sizes to suit everything from bench rework to production volume coating. Contact MTE Solutions for volume pricing on case quantities.

Shop MG Chemicals 422B at MTE Solutions:

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More from > Conformal Coating Electronics Assembly MG Chemicals MG Chemicals 422B PCB Protection Silicone Conformal Coating
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