MAGNAGLO 27B Water Suspendible Black Particles
Magnaflux 27B is a granular powder concentrate used to prepare water based black ink for wet method magnetic particle testing. The ink is used in conjunction with suitable magnetizing equipment to locate fine surface and slightly subsurface discontinuities in ferrous materials. Typical defects found include shrink cracks, welding defects, grinding cracks, quenching cracks and fatigue cracks.
Inks made from 27B give clear black indications when viewed in daylight.
Composition
27B is composed of black magnetic oxide, water conditioner, surfactants, corrosion inhibitor and foam control agents.
Typical properties
| Property | 27B |
|---|---|
| Form Granular | Powder |
| Colour | Black |
| Bulk Density | 1.2 g/cm3 |
| Recommended Concentration Range | 20.0 g per litre of water |
| Settlement Volume | 1.5 - 2.0 ml |
| pH (1% Solution) | 9.1 |
Bath Preparation
The recommended concentration is 20.0 g of 27B per litre of water.
Prepare the ink by weighing out the appropriate amount of 27B powder then adding to the correct volume of water. Allow to mix for approximately 30 minutes or until fully dispersed. Warm water can be used to aid the dispersion process.
Before use check for correct settlement volume.
Method of Use
Components should be cleaned prior to testing to reduce the risk of bath contamination and to provide a suitable test surface.
The Ink can be applied by spraying, immersion or flooding.
The ink must be mixed thoroughly prior to use and must be kept agitated during testing.
Using the wet continuous method, the ink is applied to all surfaces of the component during magnetization.
The indications will be formed during the application of magnetising current.
The flow of ink must stop before the magnetising current otherwise there is a risk that the force of the ink application may wash away indications.
Using the wet residual method, the premagnetised part is immersed in the bath, removed, allowed to drain and then inspected. This method is generally less sensitive than the continuous method and is more susceptible to rapid particle depletion and bath contamination.
In situations where the test surface colour is dark, a thin coating of a suitable white contrast paint such as Magnaflux WCP-2, may be applied prior to testing to provide a contrasting background.
Bath replenishment / Concentration control
The bath strength should be maintained constant at all times to insure consistent results.
In use the magnetic content of any ink will become depleted. To guard against this the bath strength should be checked at make up and at least once each day. The most widely used method of control is by settlement volume using a graduated ASTM pear shaped centrifuge tube.
When the settlement volume approaches the lower limit then additions of Magnaflux 27B powder can be made to the bath providing the bath liquid is still clean and uncontaminated.
If the bath appears contaminated or has been in use for any length of time, it should be replaced.
Contamination can be checked by noting the amount of foreign material that settles out with the particles in the centrifuge tube. While the particle breakdown can be observed by viewing the bath on a Ketos ring and evaluating the efficient formation of indications. If the background of the bath is such that indications cannot be readily observed, the bath should be changed.
After inspection the components should be properly demagnetized before cleaning to insure ease of particle removal.
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