Product Data Sheet – MAGNAVIS 7HF, WB-27

Visible Magnetic Inks

Chemical product icon - visible magnetic

General Description

MAGNAVIS® 7HF and WB-27, our visible magnetic inks, are used for wet method magnetic particle testing of ferrous materials. They give clear black indications when viewed in daylight.


When used in conjunction with suitable magnetising equipment, MAGNAVIS 7HF and WB-27 will locate fine surface and slightly subsurface defects such as: shrink cracks, welding defects, grinding cracks, quenching cracks, and fatigue cracks.

Typical Properties (not a specification)

Property 7HF WB-27
Description An oil-based, ready-to-use black ink. A liquid concentrate used to prepare water-based black ink.
Composition A suspension of magnetic particles in a high-flash petroleum distillate. Black magnetic powder, wetting agent, defoamer and corrosion inhibitor.
Flash point > 93°C (bulk product) N/A
SAE sensitivity 6 – 7 6 – 7
Viscosity 2.5 mm²/s at 38°C
Density 0.8 g/cm³ 1.4 g/cm³
Particle size range 0.2 – 2.0 µm 0.2 – 2.0 µm
Settlement volume (1 hour) 1.5 – 2.4 ml 1.5 – 2.4 ml
pH (2% solution) Neutral 9.0
Storage temperature 10°C to 30°C 10°C to 50°C
Usage temperature -5°C to 70°C 5°C to 80°C

Like all Magnaflux materials, MAGNAVIS 7HF and WB-27 are closely controlled to ensure batch-to-batch consistency, optimum process control and inspection reliability.

General Method of Use

Clean the component before testing to reduce the risk of contamination and to provide a suitable test surface.

If the test surface is a dark colour, apply a thin coating of a suitable white contrast paint, such as MAGNAVIS WCP-2, to provide a contrasting background.

If using WB-27, make up the ink bath based on the guide volumes below (7HF is supplied ready-mixed so you can skip this step).

Quantity of WB-27 Quantity of water
0.5 litres (500 ml) 25 litres
0.75 litres (750 ml) 37.5 litres
1 litre (1000 ml) 50 litres

Before using, agitate the ink to ensure uniformity of mix and check the correct settlement volume (see ‘Typical Properties’ table above).

Apply the ink by spraying, flooding or immersion, depending on your chosen method:

Wet continuous method

Apply the ink to all surfaces of the component and apply a magnetising current. Remember to stop the flow of ink before the current is switched off, otherwise there is a risk that the force of the ink flood may wash away indications.

Wet residual method

This method is generally less sensitive than the continuous method and is more susceptible to rapid particle depletion and bath contamination.

  • Pre-magnetise the part that needs to be tested.
  • Imerse the part in a bath of the ink.
  • Remove it and allow it to drain.
  • Inspect the part.

Remember to agitate the ink regularly during use to ensure uniformity of mix. If you are using a bath and it appears contaminated, or if it has been in use for a long time, replace the contents.

During use, the magnetic content of any ink (except for aerosols) will become depleted so you will need to check your bath strength at least once each day. The most widely-used way of checking an ink’s settlement volume is by using a graduated ASTM pear-shaped centrifuge tube.

WB-27 only: if the settlement volume approaches the lower limit (see the ‘Typical Properties’ table above), you can add more WB-27 to the bath as long as it is still clean and uncontaminated.

After inspection, remember to completely demagnetise your components before cleaning, to ensure easy  removal of any residual powder particles.

Specification Compliance

Specification 7HF WB-27
AMS2641 Yes
AMS3041 Yes
AMS3042 Yes
AMS3043 (Aerosols only) Yes
ASME B & PV Code, Sec V Yes Yes
ASTM E709 Yes Yes
ASTM E1444/E1444M Yes Yes
EN ISO 9934-2 Yes Yes
GOST R ISO 9934-2-2011 Yes Yes
MIL-STD-271F Yes
MIL-STD-2132D Yes Yes
NAVSEA 250-1500-1 Yes
SAE AS4792 Yes

Recommended Products

Product type Product name(s)
White contrast paint MAGNAVIS® WCP-2
Water bath additives  MAGNAFLUX® WA-1, WA-2
Cleaner/remover SPOTCHECK® SKC-S
Centrifuge tube for fluorescent ink (part no. 044C005)

Health & Safety

Read the relevant Safety Data Sheets for these products before use.

Case Studies


Download this Product Data Sheet as a PDF


Part number 008A103
x 10

Packaging icon: 400 ml aerosol can


Part number 058C036
x 6

Packaging icon: 1 litre plastic bottle