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An introduction
Elcometer 1120 Salt Cabinet - Corrosion Resistance Testing
Elcometer 120 Solar Box - Radient Exposure - Xenon Light Source
Elcometer 1250 Kesternich Chamber - Water Resistance Testing - SO2 and CO2
Elcometer 1537 ISO Scratching Tool
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An introduction
Testing of coatings for their resistance to environmental elements involves:
- natural weathering tests
- accelerated weathering tests
- biological deterioration tests
- chemical resistance tests
- heat resistance and flame retardation tests
- water-resistance tests
Each of the above mentioned subjects require very specific tests and as a consequence very specific instrumentation.
Tests might be performed on free films, dry films on a substrate or wet films.
Tests are performed for quality control in manufacturing as well as for R&D purposes, usually as a pass or fail test. In some cases may the degree of failure be evaluated.
The results of most test procedures cannot be expressed as a period of exposure to water in a natural environment as long as the correlation has not been established.
Natural weathering tests
Variations in the temperature, sunlight exposure, moisture and pollution profile of natural weathering tests are determined by the climate type and the seasons. Instruments must be available to monitor these parameters. The racks used to mount the samples allow different exposure angles e.g. 45° South, 90°, Station Latitude (angle equals the geographical latitude of the test station), etc.
To accelerate the effects of weathering elements, natural weathering is combined with techniques as periodically repeated salt or water spraying or concentrating solar radiation by means of Fresnel reflectors water.
Accelerated weathering tests
Accelerated weathering tests should only be used to support comparison studies as direct correlation to natural weathering has not been found for the existing equipment.
Sunlight is simulated by all kinds of lamps as xenon arc, carbon arc or the open-flame carbon arc. Lamp stability is often a problem and the use of control devices is therefore highly recommended.
Moisture is an important factor in paint degradation. Permeation of the water might cause the coating to swell during the wet cycle. If followed by a dry cycle the coating might shrink again. If a coated sample is opposed to a number of wet-dry cycles, cyclic stressing of the coating, by this repeated swelling-shrinking, might cause damages to appear (cracking, peeling, checking).
Elevated temperatures cause the degradation of coatings to occur more rapidly. Different expansion and contraction of coating and substrate might create stresses leading to cracking, peeling or checking. Testing of coatings at excessive temperatures can cause unreasonable failures.
Water-Resistance testing
The effect of water on coated samples is explained in previous item.
Studies in the US have shown that objects placed outside were wet during 30% of the time! Water originates from dew or condensation, rain, splashes, snow or ice.
Moisture can be applied to the coating in several ways: spraying, fog, condensation or immersion. Water may permeated by or pass through the coating. If water passes through the coating it might react with the substrate destroying the bound coating-substrate. The water passed through might built inclusions between coating and substrate or otherwise may it corrode the substrate.
Damages affected by moisture can result from defiencies in the coating itself, from onvolledige surface treatment or gebrekkig substrate material (e.g. contaminated).
To test the water resistance of coatings different techniques are available: immersion testing - water fog testing - condensed water - controlled condensation - cycled testing
Immersion Testing
The samples are partially or completely immersed in water. By changing the time of immersion and/or the water temperature test conditions can be changed.
Water Fog Testing
The apparatus used to test coatings for their behaviour in fog is similar to that used for salt spray tests.
Condensed Water
The sample is introduced into a chamber in which water is heated at the bottom of the apparatus. The water vapour (which is saturated) rises and condensates at the cooler part of the apparatus and onto the samples.
Influence of pollution
The influence of pollution, such as SO2, is studied by injecting small amounts of the pollutant into the apparatus. The test might be combined with the condensed water test. The presence of water might increase the effect of the pollutant onto the coating.
Salt Fog Test
Testing the resistance is important for coatings used in marine, automobile and aircraft industry as salt can cause severe corrosion of metallic objects. Tests are performed in salt fog test chambers which are described by several standard test methods as DIN, ASTM, ISO and AFNOR.
A review of test films preparation techniques is available in following literature:
Paint and Coating testing Manual - J.V. Koleske, Editor - 1995 - Chapter 37 - Film preparation for coating tests - Robert D. Athey, Jr
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Corrosion Resistance Testing
The Salt Spray Tester Elcometer 1120 BS1 consists of:
A large cabinet made of smoothly finished fibreglass reinforced polyester containing:
- the control panel with a two line LCD-display
- the electrical circuitry
- the compressed air saturator
- the salt solution peristaltic pump
An exposure chamber with water slot and covered by a pyramidically shaped, transparent Plexiglas cover
A solution tank with filter
Specifications
Exposure chamber
- Made of smoothly finished fibreglass reinforced polyester
- Heated by heating textile affixed to the exterior. PID control from ambient temperature up to 50'C. Safety device and alarm. Independent thermal switch.
- PT 100 sensor. Accuracy: ą 1'C.
- Compressed air inlet.
- Exhaust vent
Salt Solution Circuit
- Tank: with integrated filter - contents 200 l - low level indicator in the cabinet.
- Salt solution supplied to nozzle by peristaltic pump - automatic stop after 72 hrs without refilling brine tank
Compressed Air Supply
- Compressed air distribution cock with filter, pressure regulator and manometer.
- Compressed air supplied to the spray nozzle by electromagnetic valve.
- Operating pressure air: min. 2, max. 8 bar
- Compressor not included
Compressed Air Saturator:
- Resistance heater in stainless steel.
- PID control from ambient temperature up to 70'C. PT 1 00 sensor. Accuracy: ą 1'C. Safety device and alarm, refilling-dependant.
- Includes safety valve, maximum level detector, heating element, electromagnetic valve (inlet for water).
Electrical connections:
- 400 l: 220 V - 50 Hz monophase - 2000 W
- 1000 l: 220 V - 50 Hz monophase - 3000 W
- 2000 l: 220/380 V - 50 Hz threephase - 5000 W
Standard accessories:
- 10 fastening bars
- 2 sample racks
- 2 rain gauges.
Advantages
- The Elcometer 1120 BS1 is available as a basic version as well as a highly sophisticated test apparatus (by adding to the basic instrument a selection out of the numerous accessories).
- Before it is decided to use a material or part in the Elcometer 1120 BS1, it has been tested in our laboratories for its applicability in salt spray test equipment.
- Elcometer is an active member of the "Club BS" and is participating in a number of test programmes.
- Elcometer has over 15 years of experience in building and servicing test equipment
The Laboratory Pre-Installation Requirements
Products, Options & Accessories
Literature
- ASTM B 117 - 97, Standard Practice for Operating Salt Spray (Fog) Apparatus
- ASTM B 368, Standard Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
- ASTM D 1735 - 92, Standard Practice for Testing Water Resistance of Coatings Using Water Fog Apparatus
- ASTM G 85 - 94, Standard Practice for Modified Salt Spray (Fog) Testing
- DIN 50 021, Spray tests with different sodium chloride solutions
- DIN 53 167, Paints, varnishes and similar coating materials; salt spray test on coatings.
- ECCA - T8 [1996], RESISTANCE TO SALT SPRAY FOG
- ISO 7253, Paints and varnishes - Determination of the resistance to neutral salt spray (fog)
- NF ISO 9227, Corrosion tests in artificial atmospheres - Salt spray tests.
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The Elcometer 120 Solar Box (Radient Exposure - Xenon Light Source)
Description
A compact apparatus, equipped with an air-cooled Xenon light source, for evaluating the ageing effects of solar light on numerous materials.
Specifications
- Irradiation adjustable from 250 to 800 W/m˛
- 4 UV filters are available. Standard is a 280 nm filter supplied to simulate exposures at high altitudes.
- 4 models are available:
- 2 manually controlled models, 1500 or 2500 Watt, equipped with timer.
- 2 programmable models, 1500 or 2500 Watt, microprocessor controlled. This instrument contains a memory for 15 programs, a digital display, the regulation of temperature (35 - 100 °C) and irradiation on black panels and an RS232 output for PC or printer.
Advantages
- Compact unit.
- Offering a lot of test capabilities for a small price.
- Instrument of interest to many industries.
- Products that might be tested for their resistance to intensive irradiation (especially UV-irradiation) are: paint coatings, varnishes, anodised films, adhesives, plastics, paper, textiles, rubber and leather.
Operation & Maintenance
- Refer to the Standard Test Methods.
Products, Options & Accessories
Optional filters:
- 300 nm filter: to cut off all irradiation under 300 nm
- 310 nm filter: to cut off all irradiation under 310 nm
- IR filter: to reduce sample heating
Multimeter with choice of sensors to measure the irradiation density.
Flooding system for wetting specimens
Temperature probe
Humidity probe.
Literature
- Paint and Coating testing Manual - J.V. Koleske, Editor - 1995 - Chapter 52 - Natural Weathering - Lon S. Hicks and Michael J. Crewdson
- ISO 2809, Light fastness of interior paints
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The Elcometer 1250 Kesternich Chamber (Water Resistance Testing - SO2 and CO2 )
Description
An apparatus to test the resistance of material to humidity with or without the presence of corrosive gases as SO2 or CO2. It consist of a chamber with a capacity of 300 l. A glass door permits the visible control of the functioning. Digital display.
Specifications
- Constructed in reinforced polyester.
- Capacity of 300 l.
- Regulated temperature up to 50 °C.
- Ambient or saturated environment.
Advantages
- The apparatus is made conform many Standard Test Methods.
- This test offers additional information to salt spray tests.
- The corrosive gases can be injected easily.
Operation & Maintenance
Instructions how to prepare test samples are explained by several standard test methods.
The bottom contains heating elements and is filled with water. The test can be performed in different ways:
- Condensed water - continuously: 40 °C and 100% humidity.
- Condensed water - cycling conditions: 8 h 40 °C / 100% humidity followed by 16 h room temperature (18 - 28 °C) / 100% humidity
Depending on the standard test method applied the humidity conditions can be different, e.g. 50%.
In some test is a exact amount of SO2 injected in the test chamber.
Products, Options & Accessories
- Temperature extension to 60 °C.
- Automatic ventilation.
- Gas dosing device.
- Cycle counter.
Literature
- Paint and Coating testing Manual - J.V. Koleske, Editor - 1995 - Chapter 57 - Water-Resistance Testing of Coatings - Wayne Ellis
- DIN 50017, Climates and their technical application; condensated water containing climates
- ASTM G 87 - 97, Standard Practice for Conducting Moist SO2 Tests
- ASTM D 2247 - 94, Standard Practice for Testing Water Resistance of Coatings in 100% Relative Humidity.
- ISO 4623, Paints and varnishes - Filiform corrosion test on steel
- ISO 6270, Paints and varnishes - Determination of resistance to humidity (continuous condensation)
- ISO 11503, Paints and varnishes -Determination of resistance to humidity (intermittent condensation)
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Elcometer 1537 Scratching Tool
Description
A cutter made of tungsten carbide fitted to a handle.
Specifications
- Tungsten carbide blade
- 90° cutting angle
- 75° cutting edge
Advantages
Long lasting blade due to the very hard material (tungsten carbide).
Operation & Maintenance
Take care to have a minimum distance of 25 mm between two scratches or between a scratch and the edges of the test sample. One or two scratches should be made parallel to the longest side of the panel.
The scratch must expose between 0,3 and 1 mm of support material.
In case of aluminium support, one scratch is made parallel to the direction of the coil, the second perpendicular to the first.
In case of zinc plated steel support, the scratch should not cut the zinc layer.
Products, Options & Accessories
No accessories available
Literature
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corrosion - additional information