Determination of surface roughness
The roughness of the substrate after blasting must be assessed.
The used parameter is Ry5 (mean roughness depth).
The coater has the choice of the method in accordance with:
Inspection of surface cleanliness after blasting
The surface must be very thoroughly blast cleaned (Sa 2 ½) per ISO 8501-1.
Prior to an eventual chemical pre-treatment process and prior to the primer application, the surface must be de-dusted.
The remaining dust quantity and size must be evaluated per ISO 8502-3.
Therefore, the dust will be removed with a specific tape and visually evaluated. It is recommended to use a professional ISO 8502-3 Dust-Tape-Kit.
Requirements: Dust quantity and dust size must not exceed class 1
Determination of the conductivity of dripping water
The final rinse preceding the conversion bath must be done with deionized water.
The conductivity must comply with the supplier’s instructions.
The measurement with the conductivity meter includes one measurement in the rinsing-bath before rinsing and one measure of the dripping water after final rinse. Requirements: If not otherwise prescribed by the chemical supplier, the conductivity of dripping water shall not exceed 30 μS/cm at 25°C.
Assessment of stoving conditions
The temperature in the curing oven (powder coatings) and the object temperature must be measured with a 4-point measuring device.
Three detectors must be attached to the parts (in the top, middle and bottom of the oven) and one to measure the air temperature amidst the parts.
Assessment of forced drying conditions
For forced drying (liquid coatings) the temperature of the substrate in the drying oven must be measured.
This may be done by means of a 4-point measuring device, using temperature probes attached to the substrate.
Determination of dew point
The dew point is the temperature at which water condenses at the same rate at which it evaporates.
The measurement must be done with a dew point meter.
The measurement is only required if it is expected, that the temperature of the parts for before coating could possibly be below the requirements of 3°C above the dew point temperature.
This can happen if parts are stored outside in cold climate conditions or in unheated factories before blasting or before coating and the factory is not using a drying oven after the pre-treatment.
Requirements: The substrate temperature for any coating application must be at least 3°C above the dew point.
The adhesion of the coating system onto the substrate can be measured by the following methods:
For film thickness of organic layers exceeding 250 µm, only the pull-off test per ISO 16276-1 can be used.
Requirements: The cross-cut test requires a level 0 or maximum 1.
The adhesion at the pull-off test shall be higher 5 MPa.
Direct impact resistance test
The direct impact resistance is determined per ISO 6272-1 using a 20-mm diameter spherical indenter dropped under standard conditions.
For powder coatings with a thickness d≥60 µm, a mass of one kilo that falls from a height of 25 cm must be used.
Test panels must have the thickness of the parts they are linked to.
Requirements: coating systems should not show any cracking or any detachment of the coating from the substrate.
Determination of dry film thickness
The dry film thickness of the individual layers in the system and the total dry film thickness shall be measured with a thickness gauge per ISO 2808.
The measurements must be representative of the inspected area.
Per ISO 19840, the total coated surface can be used to determine the number of necessary measurements. The sampling plan consists of the number of measurements to be taken in an inspection area, and is as follows: In case of base material blasted steel the values will be corrected per ISO 19840.
surface profile in accordance with ISO 8503-1 correction value fine measured value – 10 µm medium measured value – 25 µm coarse measured value – 40 µm
The arithmetic mean of all individual dry film thicknesses is equal to or greater than the required thickness.
All individual measurements are equal to or above 80 % of the required thickness.
The arithmetic mean shall not exceed the maximum imposed by the coating manufacturer, or in absence of such a value the maximum dry film thickness (individual value) shall be not greater than three times the nominal dry film thickness
Any visual inspection of coated parts should be done at 3 m for an interior setting and 5 m for an exterior setting in diffuse daylight and with a normal unaided vision. Requirements:
At these distances and in diffuse daylight, the coating must not show any wrinkles, runs, sags, craters, blisters and other surface irregularities.
Irregularities that are an image of the steel surface or the hot-dip galvanized zinc, visible through the coating, must be disregarded.
Gloss is measured per ISO 2813, using incident light at an angle of 60°.
Note: If the significant surface is too small or unsuitable for gloss to be measured with the gloss meter, the gloss should be compared visually with a reference sample, both observed under the same viewing angle.
- Low gloss: (0 – 30) ± 5 units
- Semi-gloss: (31 – 70) ± 7 units
- High gloss: (71 – 100) ± 10 units
Wet adhesion (Boiling water or pressure cooker test)
The objective of this test is to determine the resistance of the coating system to cracking and loss of adhesion after accelerated aging by hot water.
The coater or testing lab can decide which test is preferably used.
Method 1 with boiling water: 2 hours’ immersion in boiling demineralised water (maximum 10 μS/cm at 20°C).
Remove the test sample and allow it to cool down to room temperature.
Apply an adhesive tape to the surface, ensuring that no air is trapped.
After one minute, remove the tape at an angle of 45° with a sharp even pull.
Boiling test for the approval of chromate free pre-treatments
Inspection in simmering (small to medium-sized bubbles are breaking through the surface in the complete container), deionized water (max. 10 µS/cm at 20°C).
The specimen is taken out of the water and cooled down to room temperature.
After that it is stored for 1 hour at room temperature.
The cross-cut shall be made after one hour but within two hours.
- 1. Corrosivity class 1: 15 minutes
- 2. Corrosivity class 2: 30 minutes
- 3. Corrosivity class 3: 1 hourQUALISTEELCOAT technical specification - Version 4.1 Page 45
- 4. Corrosivity class 4: 2 hours
- 5. Corrosivity class 5: 3 hours
The degree of blistering according to ISO 4628-2 must not be higher than 2 (S2).
No defects nor stripping may occur.
A certain change in colour is admissible.
The cross-cut test requires a level 0 or maximum 1.
Resistance to mortar
Per EN 12206-1 mortar is a mixture of sand, lime and water.
The mortar must be prepared by mixing 15 g of hydrated lime, 41 g of cement and 244 g of sand with sufficient tap water to make a soft paste.
Apply four portions of the mortar, approximately 15 mm in diameter and 6 mm thick, to the test panel.
Place the test panel horizontally at 38 ± 3ºC and 95 ± 5% relative humidity for 24 hours.
Then manually remove the mortar from the coated surface and remove any residue with a damp cloth.
Allow the panel to dry, and examine the coating with normal or corrected vision.
The mortar must be easily removable without leaving any residue.
Any mechanical damage to the coating caused by grains of sand must be disregarded.
The panel should not show any change in appearance or in colour after the test.
The objective of this test is to determine the corrosion resistance of the coating system.
For the corrosive categories, the test results will give an indication of the durability of the coating system.
Place the coated test piece in a spray cabinet complying with EN ISO 9227 – continuous salt spray.
After testing, remove the sample carefully from the test cabinet, wash the test panels in de-ionized water at a temperature of less than 35ºC, and dry immediately.
A cross cut test will be performed on each panel.
Assessment of corrosion and delamination at the scribe is carried out according to DIN EN ISO 4628-8.
For this purpose, it is tried to lift the coating with a sharp tool from the carved line.
- c = average corrosion of the substrate from the scribe according to ISO 4628-8 in mm
- d = average delamination according to ISO 4628-8 in mm
Number of samples: 3 panels type B for each corrosivity-category
The determination of the resistance of organic layers to humidity is evaluated per ISO 6270-1 2
Category CH: condensation atmosphere with constant humidity (also known as continuous condensation test CC).
The test is not applicable to corrosivity category C1.
The exposure time for the other corrosivity categories is based on ISO 12944-6.
Number of samples: 3 panels type B for each corrosivity category
This test simulates the resistance to discoloration and loss of gloss for an exterior use of coated products and is executed per ISO 16474-2. This test is only required for coating systems in corrosivity categories C3-C5. After 1000 h exposure, the test specimen is rinsed in demineralized water. To assess gloss and colour, mean of 10 measurements will be made on the cleaned, weathered sample and on the unexposed reference panel. Requirements: parameter measurement method acceptance criteria loss of gloss gloss measurement at 60° in accordance with ISO 2813 gloss must be above 50 % of the initial value colour change ∆E in accordance with ISO 11664-4 in accordance with acceptable ∆E values determined by QUALICOAT
The resistance of a coating system to weathering because of exposure in Florida is evaluated.
This test only applies to coating systems intended for outdoor exposure.
The test is executed by exposing the coating materials in Florida per EN 13438, A.4.8.2 and following the procedures per ISO 2810.
The test must start in April and the samples must be exposed to the elements facing 5° south for one year.
parameter measurement method acceptance criteria
loss of gloss gloss measurement at 60° gloss must be above 50 % of the initial value
in accordance with ISO 2813
colour change ∆E in accordance with in accordance with acceptable ∆E values
ISO 11664-4 determined by QUALICOAT
The low Voltage test for detecting and locating defects according to ISO 8289 is used to check that on possible sharp edges no defects occur on material for corrosivity classes C3 and above.
Measurement has to be done according to Method A with 9 Volt and wet sponge (Tap water)
For corrosivity classes ≥ C3, the entire coated surface of the objects shall be covered by the coating.
The low voltage test according to ISO 8289, using 9V DC, shall give no negative results on the entire coated surface