Group Standard Class. No.: Desc Descri ript ptor ors: s:
Issue 2008-06
50241 clea clearr coat coat,, meta metall llic ic,, pain paint, t, resi resist stan ance ce to crac cracki king ng
Testing for Resistance to Cracking
PV 1502: 1987-04, 1996-12, 2003-05
The following changes have been made as compared to PV 1502: 2003-05: –
Weather-O-Meter CI 35 test device removed removed
–
Referenced documents documents updated updated
This standard describes a procedure for testing the resistance to cracking of the clear coats used in dual-layer paint coatings. The procedure corresponds corresponds largely to the content of VDA 621-430 "Tests for Coating Methods; Tests for Resistance to Cracking of Clear Coats in Dual-Layer Metallic Metallic Paint Coatings".
Requirements Requirements according to drawing and/or TL (Technical Supply Specification).
Xenotest Beta LM or Xenotest 1200CPS by Atlas Material Testing Technology GmbH.
Page 1 of 4 Technical responsibility GQL-LP/3
Lutz Porzelt
GQL-LP
Dr. Ro Roger Hi Hillert
Standards department Tel.: +49-5361-9-75066
EKTC/4 Jürgen Wiesner
EKTC
Tel.: +4 +49-5361-9-29064
Manfred Te Terlinden
VWNORM-2007-10e
Page 2 PV 1502: 2008-06
Unless otherwise agreed, 0,8 mm thick steel panels (body panels) of a size suitable to the relevant test equipment must be used as the paint substrate. To ensure that the test results are not corrupted by the influence of corrosion, the steel panels must be protected by a primer coat. In order to ensure that t he weathering result is as close to reality as possible, the original paint structure must be used; adherence to the layer thickness acc. to Sec‐ tion 4.3 is particularly important.
In order to monitor the continuous operation of the weathering device, clear paints for which t he cracking behavior and times are known must be used. These test standards remain in the weathering device constantly during testing and are replaced when they start to crack. They are produced as follows: –
Paint substrate: 0,8-mm-thick body panel sheet metal
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Pretreatment: zinc-phosphated
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Corrosion protection: electrocoated
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Structure: Filler Base coat: silver metallic (without light stabilizers), approx. 15 µm layer thickness Clear coat: FF 68-0102 from BASF L+M, Münster Hiltrup, approx. 40 µm to 50 µm layer thickness 10 min flash-off time, then baked for 20 min at +130 °C in the mechanical circulation oven.
The aging period of the liquid paints is max. 12 months at room temperature. The aging period of the test standards is max. 24 months at room temperature.
The tests are preferably conducted on at least two specimen panels per paint system. The device conditions are described in Table 1. During testing it is important to ensure that no spray water stains form on the specimens. The spray water must be renewed in every rain simulation phase and must be free of reaction prod‐ ucts, abraded materials, and SiO 2.
The specimen panels are examined for the formation of cracks every 500 h (standards after 250 h, then every 24 h thereafter) using a magnifying glass (8× magnification). In cases of doubt, a stereo microscope (20× magnification) must be used. The start of cracking is the test period after which at least 10 cracks are evident on the paint surface. The type and number of cracks must be described according to DIN ISO 4628-4. Changes in gloss must be evaluated before and after weathering in accordance with DIN 67530.
Page 3 PV 1502: 2008-06
The following information must be provided in the test report with reference to PV 1502: –
Type and designation of the paint structure
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Layer thickness of the clear coat
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Start of cracking according to device hours
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Type and number of cracks
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Start of non-paint-specific cracking on blisters and foreign matter inclusions
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Change in gloss
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Other changes in the paint coating, such as yellowing or blistering
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Test date
1
Irradiation source
3 air-cooled Xenon arc lamps, 2 800 W each; Irradiator replacement: when it is no longer adjustable
2
Optical filter
2.1
Xenotest Beta LM
Xenochrom 300
2.2
Xenotest 1200CPS
2½ Suprax Drittelschalen
3
Irradiation intensity
60 W/m ² at 300 to 400 nm; Control via light monitor
4
Specimen mode
Non-turning mode
5
Bright/dark phase
120 min light phase + 60 min dark phase
6
Rain simulation cycle
40 min dry phase (with light), 20 min spraying (with light) on the front side of the speci‐ men, 60 min dry phase (with light), 60 min spraying (without light) on the front side of the spec‐ imen
7
Type of rain simulation
Spraying with de-ionized water (room temperature)
8
Specimen room ventilation
Fresh air/circulation mode
9
Black standard temperature
+73 °C to 76 °C at the end of the dry phase, +37 °C to 39 °C during the dark phase
10
Specimen chamber tempera‐ +47 °C in the light phase, ture +38 °C in the dark phase
11
Relative humidity
50 ± 5% during the dry phase, 95 ± 5% during the rain simulation and dark phases
The following documents cited in this standard are necessary for application. In this Section terminological inconsistencies may occur as the original titles are used.
Page 4 PV 1502: 2008-06
DIN 67530
Reflectometer as a means for gloss assessment of plane surfaces of paint coatings and plastics
DIN ISO 4628-4
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VDA 621-430
Tests for Coating Methods; Tests for Resistance to Cracking of Clear Coats in Dual-Layer Metallic Paint Coatings
