NDT Consumables Explained: Penetrants, Developers and Removers

Non-destructive testing (NDT) lets inspectors find cracks and flaws in aircraft parts without damaging them. Two of the most common methods — liquid penetrant inspection (PT) and magnetic particle inspection (MT) — rely on a family of consumables that must be matched correctly to work. Here is what each one does.

Liquid penetrant inspection, step by step

Penetrant inspection reveals surface-breaking defects — cracks, porosity, laps — on most non-porous materials. It uses three consumable steps in sequence:

• Penetrant is applied to a clean surface and drawn into any surface-breaking flaw. It comes in two visibility types — fluorescent (viewed under UV light, highest sensitivity) and visible/colour-contrast (a red dye seen in normal light, convenient in the field) — and in different sensitivity levels (typically 1–4).
• Remover / cleaner wipes away the excess surface penetrant without pulling it back out of real defects. Water-washable penetrants rinse off; solvent-removable systems use a dedicated remover.
• Developer draws the trapped penetrant back out and spreads it to form a clear, magnified indication. Developers come as dry powder, water-based, or non-aqueous (solvent-suspension) aerosols — the choice affects contrast and drying speed.

Magnetic particle inspection

For ferromagnetic parts, magnetic particle inspection uses magnetic powders (dry or wet, fluorescent or non-fluorescent) that gather at surface and near-surface discontinuities under an applied magnetic field. Colour is chosen for contrast against the component.

Choosing the right consumables

• Match the sensitivity to the job — critical rotating parts need higher-sensitivity fluorescent systems; general checks may use visible dye.
• Keep the family compatible — penetrant, remover and developer are designed to work as a set; mixing brands or types undermines results.
• Mind the material — low-sulphur, low-halogen products matter for nickel and titanium alloys.
• Check shelf life and traceability — expired chemistry gives false results; documentation matters for audits.

Sourcing genuine, traceable NDT chemicals

Angad Aviation supplies NDT consumables from established manufacturers with full traceability. Browse the range on our NDT Chemicals category, or request a quote for any product, pack size or lead time.