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VDA233-102 Cyclic corrosion testing of materials and components in automotive construction

VDA233-102汽車結(jié)構(gòu)中金屬和元件的循環(huán)腐蝕試驗

5 Execution

5.1 Test conditions – Test procedure The test duration is to be stipulated upon on a case by case basis. The typical test duration is six full test cycles (6 weeks). If necessary, the test duration can be changed until it is possible to draw conclusions concerning the corrosion behaviour.

Interim assessments have proven useful to determine the progression of corrosion.

A full test cycle lasts 7 (Fig. 1) days and consists of:

3 times = 24h cycle A (Fig. 2; see also 7.2) without freezing phase, with 3 h salt spray phase (1 % NaCl solution)

3 times = 24h cycle B (Fig. 3; see also 7.2) without freezing phase, without salt spray, including assessment of specimens (or walk-around inspection)

1 time = 24h cycle C (Fig. 4; see also 7.2) with freezing phase, without salt spray

Fig.1: The placement of specimens in the test chamber shall be carried out exclusively during the
first cycle B of the evaluation phase. This also applies for the removal of the specimens.

Fig.: 2: 24 h-cycle A, with 3 h salt spray phase (1 % NaCl)

Fig.: 3: 24 h-cycle B without freezing phase, without salt spray, with evaluation phase

Fig. 4: 24 h-cycle C, with freezing phase, without salt spray

5.2 Test interruption

Interruption of the test or opening of the test chamber is only permitted during the evaluation phase (cycle B). The test chamber may not be switched off during this time.

No interruption of the salt spray phase is permitted. Longer interruptions of the cyclic climate phases are to be avoided; if unavoidable, they must be mentioned in the test report.

5.3 Placing specimens in the chamber

The specimens shall preferably be positioned in the chamber at an angle of 65° to 75° relative to the horizontal with the side to be tested uppermost. Components are to be positioned as agreed with the principal, preferably in the orientation in which they will be installed. The specimens (or components) may not contact each other or shield other specimens from the salt spray.

When using two separate test chambers for the salt spray phase and the cyclic climate phase, the specimens may not be allowed to dry-out when being transferred from one chamber to the other.

Vehicle components or special corrosion test plates may also be used as specimens for the test. In the case of components, special care shall be taken to ensure that salt solution does not pool on the specimen, as this will affect the test conditions (climate). If this cannot be avoided, such pooling must be removed at least once a week.

6 Monitoring of the test system

To ensure reproducibility of the results ob-tained by one test system, or rather the comparability of the results from different test systems, it is recommended to monitor these tests regularly.

6.1 Monitoring using mass-loss specimensSubstrate, dimensions, and preparation of the mass-loss specimens are defined in DIN EN ISO 9227.

The mass-loss specimens are positioned at 65° to 75 ° relative to the horizontal. The

back-side is to be protected from corrosion attack, for example with removable adhesive tape.

The removal of the corrosion products is defined in ISO 8407.

The evaluation of the mass-loss specimens is done by the gravimeteric method, by weighing the specimens after the test. The mass-loss specimens weighed with an accuracy of 1 mg. The mass-loss (difference of mass) is to be divided by the area of the exposed surface, to get the mass-loss with respect to one square meter

If the average mass-loss of at least 3 mass-loss specimens after three cycles testing time is 900 ± 220 g/m², the testing chamber is working satisfactorily.

Note:

The fractional values for relative humidity result from the specified condition that the temperature must be ramped up (35 - 50) °C at a heating rate of 0.125 K/min and that changes in relative humidity take place at a rate of 0.1 %/min for ramps of [(100-50); (70-90;

(90- 95)] % and 0.33%/min for ramps of (50-70) %. If in doubt, the data given in section 7.2 shall apply. When temperature ramps are passed through during periods of constant relative humidity, deviations of – 8 % to + 5 % relative humidity are accepted.