PowerPoint-presentation · 2020. 8. 1. · From ISO/TR 16335 –Guidelines for selection of...
Transcript of PowerPoint-presentation · 2020. 8. 1. · From ISO/TR 16335 –Guidelines for selection of...
mars 2019
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Repositioning of test panels
during exposure – effect on
corrosivity of steel panels
Evaluation of reproducibility of
accelerated corrosion test –
ACT 1
ACCELERATED CORROSION TESTS
Accelerated corrosion testing is an essential tool for assuring
sustainability of parts and components that are exposed to
corrosive environments.
Many test methods have been developed and used over the
years.
Type of test
A Continuous salt spray tests
B Alternating exposure to salt solution or salt spray followed by drying
C Cyclic variation of humidity and including exposure of salt spray or rain
DContinuous exposure atmospheres with low concentration of corrosive gases at
moderately high humidity
EContinuous exposure atmospheres with higher concentration of corrosive gases at
higher humidity also with steps of drying and exposure to salt spray
F High humidity tests
From ISO/TR 16335 – Guidelines for selection of accelerated corrosion test for product qualification
From ISO/TR 16335 – Guidelines for selection of accelerated corrosion test for
product qualification
Field of
applicationSuitability of different categories of corrosion tests
Description
A
(Constant
salt spray)
B
(alternate
immersion/spray)
C
(humidity
cycling with
salt exposure)
D
(air pollutants)
E
(air pollutant,
drying and salt
spray)
F
(condensation)
Marine N U P P
Automotive N U P P
Building
constructionN U P P
Electric devices U* U* U* P P P
* For tightness
P: Preferred method
U: Useful for comparative tests of same product
N: Not useful unless for QC of same product
ACCELERATED CORROSION TESTS
Conclusively, the field of application determines what type of corrosion test
that should be chosen.
In many fields of application, tests using cyclic humidity and temperature with
intermittent salt exposure are being used more frequently. One of the main
reasons is that they often show good agreement with field exposures.
Salt spray tests may be used for process stability control of coatings for
cathodic protection. For product qualification, salt spray testing is not
suitable.
PURPOSE
The purpose with this study is to evaluate the
effect of periodic repositioning of the tested objects
during exposure.
The Accelerated Corrosion test method used is
described in e.g. Volvo STD 423-0014.
Standard test panels of CRS 150×70×1 mm were
used.
POSITIONS IN TEST CHAMBER
Initially, in each position (1-7) 2 sets of steel panels, A and B, respectively, with 3 panels in each set are positioned.
After each full cycle (one week), the set B panels are moved one position up (1→2, 2→3 etc).
The A set of panels are stationary during the full test.
After six weeks, the test is terminated and the weight loss due to corrosion is measured by dissolving the corrosion
products as per the method in ISO 8407 using 50ml/l HCl and 3,5 g/l hexamethylenetetramine as etchant.
2 15
6
7
3 4
↕ appr 10 cm↔ appr 10 cm
TEST CYCLE - ACT
Salt content. 1.0% ± 0.1%
pH 4.2 ± 0.1
Temperature deviation over the test plane
The temperature deviations were measured the last 5 minutes of a plateau before a ramp.
The conditions above are 35°C, 95 %RH and an empty test Cabinet.
This kind of data is very helpful to foresee corrosion scattering performance.
The temperature measurements were done by ControlArt in collaboration with Volvo Cars
RESULTS
Average metal loss ± std dev stationary panels: 162,7 µm ± 4,39 (2,70%) 1269 g/m² ± 34,2Average metal loss ± std dev repositioned panels: 160,0 µm ± 4,40 (2,75%) 1248 g/m² ± 34,3
163 160
0
20
40
60
80
100
120
140
160
180
Stationary Repositioned
µm
Metal loss
RESULTS
0
20
40
60
80
100
120
140
160
180
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Met
al lo
ss (
µm
)
Position
Stationary panels
1 2 3 4 5 6 7
Position
RESULTS
0
20
40
60
80
100
120
140
160
180
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Met
al lo
ss (
µm
)
Position
Stationary panels
0
20
40
60
80
100
120
140
160
180
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Met
al lo
ss (
µm
)
Position
Repositioned panels
1 2 3 4 5 6 7
Position
1 2 3 4 5 6 7
Position
Metal loss
It cannot be concluded that the repositioning has had an impact on the test result.
0
20
40
60
80
100
120
140
160
180
200
1 2 3 4 5 6 7
Met
al lo
ss (
µm
)
Position
Average metal loss per positionStationary
Repositioned
COMMENTS
• No significant difference between stationary and repositioned test panels.
• The purpose with this study was to evaluate the effect of periodic repositioning
of the tested objects during exposure. It cannot be shown that repositioning of test objects has any effect on the spread
in results in this type of chamber.
• It was also shown that the position in the chamber had no influence on the metal loss – the whole chamber can be used
• One cabinet only, one test period of six weeks
• Only steel panels, no zinc, no painted and scribed panels
• The cabinet had a low to medium load of parts. No parts were positioned closer than
10 cm from the test objects
• The cabinet was a ControlArt AB type TC210, installed during 2017.
• In future studies, similar measurements need to be performed in other cabinets, especially in cabinets produced by other
manufacturers.