FAQ

ST= Bare steel
HD = Discontinu hot-dip galvanized steel (according ISO 1461)
SZ = Continuously hot-dip galvanized steel (according EN 10346)
MS = Thermally sprayed part with a layer of zinc or zinc/aluminium (according ISO 2063)

These substrates can then receive different mechanical and/or chemical pretreatments and/or deposition of a colloidal organic primer before application of the liquid or powder coating system.

The QUALISTEELCOAT corrosivity class is defined by the corrosivity Category in combination with the expected lifetime high (H).

ISO 12944-2 defines 5 general atmospheric corrosivity categories ranging from C1 to C5

Corrosivity category C1 - very low
Exterior: /
Interior: heated buildings with clean atmospheres, e.g. offices, shops, schools, hotels.

Corrosivity category C2 - low 
Exterior: with low level of pollution; mostly rural areas 
Interior: unheated buildings where condensation may occur, e.g. depots, sports halls. 

Corrosivity category C3 - medium
Exterior: urban and industrial atmospheres, moderate sulphur dioxide pollution; coastal areas with low salinity 
Interior: production rooms with high humidity and some air pollution, e.g. food processing plants, laundries, breweries, dairies

Corrosivity category C4 - high
Exterior: industrial areas and coastal areas with moderate salinity
Interior: chemical plants, swimming pools, coastal ship- and boatyards

Corrosivity category C5 - very high
Exterior: industrial areas with high humidity and aggressive atmosphere and coastal areas with high salinity
Interior: buildings and areas with almost permanent condensation and with high pollution

ISO 12944-1 defines a lifetime that fixes the time until the steel parts must undergo a first major maintenance painting.

This standard durability is expressed in 4 ranges:
    low (L): 2 to 7 years
    medium (M): 7 to 15 years
    high (H): 15 to 25 years
    very high (VH): > 25 years
 

>>> The QUALISTEELCOAT corrosivity class is defined by the corrosivity category in combination with the expected lifetime high (H). <<<

The deposition layer is an inorganic layer applied or formed on the steel substrate before the organic coating system is applied. It is therefore part of the preparation/protection system beneath the powder coating or liquid paint. The current QUALISTEELCOAT Specifications 5.0.1 distinguish these pretreatment and deposited-primer steps from the subsequent organic coating system.

In practical terms, think of the system as: Base material → pretreatment / deposition layer → organic coating layer(s)

The deposition layer can provide functions such as:

1. improving corrosion protection;
2. improving the adhesion of the subsequent organic coating;
3. creating a more suitable and uniform surface for coating;
4. acting as an additional protective barrier between the steel and the organic coating.

EC = Electrophoretic deposited primer: colloidal particles suspended in a liquid medium migrate under the influence of an electric field (electrophoresis) and are deposited onto the base material. 
CP = Currentless deposited primer: colloidal particles, suspended in liquid medium, are deposited onto the base material without the support of an electric field. 

The coating system designation identifies the base material, any deposited primer, and the number of organic coating layers. 
Some examples: 

MS2 stands for metal-sprayed steel with two organic coating layers.
STCP3 stands for a steel with a currentless deposited primer and two additional organic coating layers. (3 organic layers in total)

Pre-treatment prepares the base material for the application of the coating system. It may be chemical, mechanical, or a combination of both. When choosing a chemical pre-treatment, always check that it is approved by QUALISTEELCOAT.

The UV class is a classification indicating the resistance of an organic coating to UV radiation and its ability to retain colour and gloss during outdoor exposure.

For example, UV Class 2 provides better long-term colour and gloss retention than UV Class 1, making it more suitable for demanding outdoor exposure.

The finish defines the final appearance of the coated surface and is generally specified by the customer or project requirements. The coater applies the prescribed finish using an appropriate approved coating system. Typical finishes include gloss, satin, matt and textured.

Gloss: a smooth, highly reflective surface
Satin: a smooth surface with a moderate, semi-gloss appearance
Matt: a low-gloss surface with little reflection
Textured: a surface with a deliberately structured or textured appearance

Metallic is slightly different. This is an effect/appearance rather than a gloss-level finish, because a metallic coating can itself be gloss, satin or matt.

Ask for the QUALISTEELCOAT certificate. Every certified coater has an official certificate with a unique E-... licence number, clearly stating the coating systems covered by the certification.

The QUALISTEELCOAT certificate is valid for one year. Its validity is renewed annually, subject to a successful audit confirming that the coater continues to meet the QUALISTEELCOAT requirements.

Approved coating materials are identified by a QUALISTEELCOAT approval number. The approval number starts with:

PE- for Powder Exterior
LE- for Liquid Exterior

Always check that the coating material has a valid Qualisteelcoat approval for the intended application.

Approved chemical pre-treatments are identified by a QUALISTEELCOAT approval number starting with CE. Two approval routes are available:

Track 1: approval based on documented experience (minimum 1 coater with QUALISTEELCOAT license using the product)
Track 2: approval based on testing results demonstrating the performance of the pre-treatment

For objects that have to comply with EN 1090, sharp edges are not allowed for C3 or higher. Qualisteelcoat refers to the coatability of the parts and the prepartion grade.

A mono-layer coating system can’t cover sharp edges in an adequate way. 
It is highly recommended to apply a multi-layer coating system to protect the borders, cuts, punches and welding against corrosion.

To ensure that the organic layer provides sufficient protection, the applicator can control the coating layer with the pinhole detector with wet sponge technique at the critical zones at 9V. The coating should be free of pores, alsoon the edges. This test is in accordance with ASTM D5162 –08 Standard Practice for Discontinuity (Holiday) Testing of Nonconductive Protective Coating on Metallic Substrates.

It is recommended that suspension points will be properly touched up too.

Before applying a coating system, it is important to verify that the steel structure is suitable for coating. The design, condition of the steel surface, accessibility, welds, edges, corners and other construction details can all influence the quality and durability of the coating.

The following questions should be considered to evaluate the suitability of an object for the application of a coating system:

1. Is the pre-treatment process adapted to the work piece?
2. Can the coating system be applied to this substrate?
3. Is the paint system suitable for the corrosivity category?
4. Is the preparation grade suitable according to the table below?

Doubts about the suitability of the object for the application of the considered coating system must be discussed with the customer. A written agreement must then be available.

Apart from that for load bearing structures according EN 1090-2 (material ³ 4mm) with an expected corrosivity category from C3H and higher the preparation grade in accordance with ISO 8501-3 preparation grade must fulfil the requirements shown below. 

P1 - Light preparation
P2 - Thorough preparation
P3 - Very thorough preparation

Corrosivity category       Preparation grade
C1                                  P1
C2                                  P2
C3                                  P2
C4                                  P2 or P3 as agreed between parties
C5                                  P2 or P3 as agreed between parties