Page 226 - Welding of Aluminium and its Alloys

206 The welding of aluminium and its alloys

Penetrant
Defect open to surface

Penetrant drawn into
defect

Penetrant cleaned off Penetrant drawn out
but retained in defect and staining developer

Developer sprayed on

Beam of fluorescent light
Dye fluorescing

Fluorescent dye retained
in defect

11.9 Penetrant examination principles.

11.10 Liquid penetrant test result illustrating staining of the spray-on
developer by a defect in the HAZ. Courtesy of TWI Ltd.

method. Wire brushing or grinding should not be used unless it can be fol-
lowed by an acid etch as mechanical methods of cleaning can smear over
defects and prevent the dye from penetrating.
Inspection in other than the flat position is difficult but penetrants have
been developed with a jelly-like consistency that can be used to carry out
inspections in the vertical and overhead positions.Automated methods may
be used, with the components loaded into baskets and processed on a con-