VOLVO STD 1021-2 Drawing of Surface Coated Test Objects and Evaluation of Corrosion Propagation from the Drawn Line in Corrosion Test

The standard “VOLVO STD 1021-2 Scribing of surface coated test objects and evaluation of corrosion propagation from the scribed line in a corrosion test” developed by the Volvo car company describes a method of introducing defined damage to organic surface coatings on metal surfaces using a hand-held scribing tool. The damage is done to expose the base material for evaluation of corrosion protection in a subsequent corrosion test.

The orientation of the plotted lines is often quite important for the test results in corrosion testing. In panels slightly inclined from vertical, more salt will collect in a horizontally exposed line than in a corresponding diagonal or vertically exposed line.

Another difference is that a horizontally drawn line will produce a uniform salt load, whereas a diagonal and especially vertically drawn line will tend to produce a slope with increasing amounts of salt along the lower edge of the line. Increasing amounts of salt generally lead to a more rapid corrosion process, but on painted steel, high salt exposure can have an inhibitory effect on corrosion because the corrosion products formed are so concentrated.

Components should be placed or drawn on the component in such a way that the orientation of the drawn lines corresponds to the requirements for flat panels as much as possible.

Drawing is done with a drawing apparatus equipped with a flat, shaved drawing steel. Such an apparatus ensures a relatively constant width of the uncoated metal surface, while the penetration depth is small compared to the width of the drawn line. A controlled area per unit length of the drawn line is important in many respects and is crucial for meaningful test results for painted, galvanically sacrificial metallic coatings (e.g. zinc).

The scribing tool uses high-speed steel in its design. The edge width is 0,50 mm plus/minus 0,02 mm for painted test objects. For test objects with other surface coatings (e.g. sealants or rust inhibitors), it is 1,00 mm plus/minus 0,02 mm.

There are several possible designs of a complete scribing device. The handheld device should preferably be provided with lateral support to ensure consistent scribing execution. The angle of the scribing steel should preferably be locked by a recess in the handle. An example of a handheld device with high speed steel as described above is shown in the standard.

The scriber is applied with an edge angle of 80 degrees plus/minus 5 degrees in the direction of the scribed line and 90 degrees plus/minus 3 degrees on the sides. In order to remove sharp burrs that may tear the paint coating, a new tool steel should always be broken by making at least 10 test drawings on a painted steel panel. During drawing, each line should be drawn until metal chips are formed. The drawing angle requirements should be maintained as much as possible when drawing curved surfaces. Complex test objects where there is insufficient space for the scriber can be drawn using a wedge-tipped carbide scriber with a tip width of approximately 0,2 mm. Due to the undefined exposure area of ​​steel substrates, the wedge-tipped tip of the scriber should not be used on galvanized materials.

The condition of the steel is checked in the scribing apparatus by drawing a line on a painted steel panel. A sufficient number of scribing operations must be made for metal shavings to begin to form. If the lower width of the scribed line is less than 0,4 and 0,8 mm respectively, the tool steel must be replaced.

Among the numerous testing, measurement, analysis and evaluation studies that our organization has carried out for businesses in various sectors, our organization also provides testing services defined in the standard “VOLVO STD 1021-2 Drawing of surface coated test objects and evaluation of corrosion propagation from the drawn line in corrosion test” with its trained and expert staff and advanced technological equipment.