VR211 - For the Use of IGP-KORROPRIMER
Introduction
IGP-KORROPRIMERs have been specially developed to provide extended protection against corrosion. All IGP powder coatings, and water- and solvent-based top coats are suitable for use as top coats. An adhesion test must be done for these liquid varnish systems.
IGP-KORROPRIMER is available in the following versions:
An Overview of the Product
1. Pay attention to the accompanying documentation such as the Technical Data Sheet and the Safety Data Sheet.
2. Work cleanly – the surfaces to be coated should only be touched while wearing gloves.
3. Only faultless powder coated surfaces provide lasting protection against corrosion.
4. The usual parameter settings apply for application of the powder.
5. The prescribed layer thicknesses are between 60 and 100 μm and depend on the corrosion category. These are described in DIN EN ISO 12944 and DIN EN ISO 55633. Alternatively, use the IGP recommendations from the IGP corrosion protection matrix – see the appendix.
6. Pay attention to the maximum oven temperatures and oven times indicated in the Technical Data Sheet (see point 4 in this processing instruction).
As an alternative to complete curing, IGP-KORROPRIMER can be gelled only. ‘Gelling’ is defined as reaching the possible temperatures indicated in the range of curing temperatures for short periods. If a liquid varnish is to be used as a subsequent top coat, the primer used must be completely cured.
Detailed Process Description
Introduction
IGP-KORROPRIMERs are zinc-free priming powders that have been specially developed for heavy-duty protection against corrosion for steel and aluminium products. System elements with steel primer and suitable top coat system satisfy the most corrosion protection categories depending on the quality and method of preparation and pre-treatment. You can find the IGP recommendations for layering coatings in the corrosion protection matrix in the appendix.
When processing IGP-KORROPRIMERs you must always comply with the Technical Data Sheet and the corresponding Safety Data Sheet. The standard ‘Corrosion protection of steel structures by protective paint systems’ DIN EN ISO 12944 should be used as the basis for working with IGP-KORROPRIMER. We also suggest using the recommendations in DIN 55633 ‘Corrosion protection of steel structures by powder coating systems’ as a guide.
Substrates, Preparation and Pretreatment
All substrates to be coated must be free of oxidation products, residue from scale, oil, grease and release agents. The substrates must not have any sharp edges (radius less than 2 mm). Laser-cut edges, weld points and weld seams must be sandblasted or chemically scoured prior to coating.
Steel Pre-Treatment
2.2.1. Cleaning and Degreasing
All conventional degreasing baths or sprayers are suitable for cleaning and degreasing. A faultless preliminary clean is essential for good corrosion protection.
2.2.2. Blasting
All conventional blasting procedures can be used for the pre-treatment. After blasting, the workpieces should have a standard purity grade of at least SA 2.5 ‘bare metal’ in accordance with DIN EN ISO 12944-4. Sharp edges and the like must be avoided. After blasting the measured surface roughness Rz must be between 40 μm and 60 μm. The coating thickness for the primer must be greater than the surface roughness in μm to ensure that all peaks are covered.
2.2.4. Sweeping (Sweep Blasting) for Galvanised Surfaces
All conventional sweeping procedures can be used. The blasting material must not contain any metallic components when sweeping zinc substrates. Ideally, fused corundum is used.
2.2.5. Chemical Conversion
All conventional sweeping procedures can be used. The blasting material must not contain any metallic components when sweeping zinc substrates. Ideally, fused corundum is used.
Pre-Treatment of Aluminium
2.3.1. Chemical Conversion of Aluminium
All conventional chromating and suitable chrome-free alternatives can be used for chemical conversion. The suitability of alternative procedures for providing an adhesion primer for IGP-KORROPRIMER should be checked beforehand (adhesion test, pressure cooker test and cross-cut adhesion test in accordance with GSB, QUALICOAT).
2.3.2. Pre-Anodising
Experience shows that pre-anodising with optional post-purging solution as a pre-treatment method achieves the best results against filiform corrosion. We recommend regular adhesion testing of the layered coatings (pressure cooker test and cross-cut adhesion test in accordance with GSB, QUALICOAT).
Corrosion-protection-compliant reprocessing of components Edges:
Sharp edges such as those caused by cutting, drilling, punching and sawing of sheets must be rounded. This avoids excessive pulling back of the powder primer from the edge (edge retreat) during the curing pro-cess. Edges that are optimally prepared for coating should have a radius that is no less than 2 mm.
Gaps:
Gaps must be avoided during initial design of the component as dirt and moisture may accumulate here. Primer powder can only penetrate gaps with difficulty. Present protective greases and oils may escape from gaps and overlaps and can drastically impair the coating result.
The Coating
IGP-KORROPRIMER can be applied with all conventional powder coating systems (corona or tribo charging). Coat thicknesses between 60 and 100 μm are recommended (depending on the corrosion protection category). For processing with corona pistols, a high voltage setting between 60 and 100 kV is recommended to achieve good levels of application efficiency. For finishing and complex geometries, high voltage settings between 40 and 50 kV can also be used. For complex geometries and a high penetration capacity, application with tribo charging is recommended. For ultrasonic sieving, we recommend using sieves with grid sizes greater than 140 μm.
Recovered powder can be fed back into the application process as fractions without any problems. If IGP-KORROPRIMER is to be used as a finish over itself, e.g., to achieve very thick coatings, the first coating should only be gelled (see number 4).
For finishing with liquid coating systems, IGP-KORROPRIMER must be completely cured. Each coating system must also be checked for intercoat adhesion prior to use as a top coat.
Top coating with liquid coatings
We recommend in principle sanding the IGP-KORROPRIMER coat for optimal adhesion.
Curing
If a top coat with powder is to be applied immediately after priming, we recommend only gelling the IGP-KORROPRIMER. ‘Gelling’ is defined as reaching the possible temperatures indicated in the range of curing temperatures for short periods. Ensure the maximum circulating air temperature is not exceeded (see table).If the furnace retention time is too long, this can lead to a loss of intercoat adhesion. Therefore, we particularly recommend gelling in the case of thick materials (thicknesses greater than 3 mm). The primer is also cured as a result of the curing process of the top coat system. Pay attention to the adjusted curing temperatures for
IGP-KORROPRIMER and the top coat system. To take full advantage of the outgassing-friendly
properties of IGP-Korropirmer V, it is recommended that
the V variant on substrates that are sensitive to outgassing.
burned in.
If a top coat is not immediately applied afterwards, the temperature / time information in the Technical Data Sheet must be complied with. To prevent losses of intercoat adhesion, the maximum residence time and the maximum circulating air temperature in the oven must not be exceeded.
* recommended curing conditions for 100% crosslinking.
For directly heated gas ovens (depending on gas quality and oven layout), there may be intercoat adhesion losses when reaching the maximum residence times at object temperature. Check the adhesion regularly.
Instructions for Quality Assurance
Working Cleanly
A clean working environment is required when working with IGP-KORROPRIMER. This is particularly important when working with highly active substrates such as pickled aluminium or blasted steel, for example (wear gloves!). Primed workpieces that are to be given a top coat should not be touched with bare hands.
Follow-up Processing
In the interest of maintaining corrosion protection, no subsequentmachining (e.g., forming, milling, and drilling) should be carried out on coated steel parts.
Storage of Powder
Pay attention to the shelf life of the IGP-KORROPRIMER, particularly the reactive low-temperature coatings. IGP-KORROPRIMER should be stored in a dry place away from direct sunlight, at temperatures below 25 °C. Storing large or unwanted quantities of primer material in the coating area and especially in the immediate vicinity of the stoving oven must be strictly avoided.
Storing Coated (Primed) Parts
A maximum interval of 24 hours should be allowed to elapse between the priming process and subsequent application of the top coat. Generally speaking, it is advisable to follow the priming process immediately with application of the top coat. Top coats should be applied within 6 hours on substrates whose primer coat has only been gelled.
If possible, primed components should not be stored. If, however, they must be stored, the following points must be observed:
- The components must be stored somewhere dry and clean
- Where possible, the storage temperature should be between 20 °C and 30 °C
- The components must be stored so that UV radiation / sunlight is excluded
- Pay attention to and prevent possible formation of condensation due to high temperature differences
- For primed piece goods which have been stored for more than 24 hours, appropriate cleaning is recommended
Disclaimer
The verbal, written and experimentally derived advice related to application we provide is based on the best of our knowledge but must be considered non-binding information and does not release you from your responsibility to conduct your own testing. The application, use and processing of our products occur outside our possibilities of control and are therefore exclusively your responsibility.
