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Main Articles Polymer coatings for steel façades and roofs
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Polymer coatings for steel façades and roofs

Polymer coatings for steel façades1
14.09.2019

Polymer-coated galvanized steel façades and roofs are the best solution used in construction of buildings due to their long life, excellent appearance, and cost-saving. Correct choice of polymer coating ensures high durability and reliability of products.

Polymer-coated steels for roofs and façades by Ruukki-SSAB are developed with account of the possibility of usage in any application severities. Roof and façades are affected by the sun, frost, pollutants contained in the air, mud, rains, snowfalls, strong winds, and sometimes hurricanes. In this case, good quality coating preserves the initial appearance and properties of products for a long time. Roof and façade steel by Ruukki has excellent shaping capacity and can be processed even at low temperatures.

 

When selecting polymer coating for construction materials, it is important to take account of the building operation period, climatic and operational conditions of the environment, as well as other possible special requirements. From among the broad range of coatings offered by Ruukki, one can choose the most suitable option, enabling to achieve the necessary long life and excellent appearance of the building.

 

Environmental conditions

 

The environmental conditions have a substantial impact onto the choice of polymer-coated steel. Solar UV irradiation affecting the coating, gradually changes the chemical composition of paint, which may result in weakening of the gloss effect, colour fading, as well as worsening of the anti-corrosion protection.

 

Apart from that, moisture, heat, atmospheric pollution, and other compounds affect corrosion resistance of steel. For various operational conditions, it is recommended to select the relevant polymer coatings. Coated galvanized steel can be used in corrosivity categories C1-C4, while usage in category C5 is considered individually for particular operation conditions. Atmospheric load is determined under DSTU ISO 12944-2:2019.

 

Corrosivity category means atmospheric conditions as per DSTU ISO 12944-2:2019

Corrosivity category

Environment
ExteriorInterior
C1
very low

Heated premises with clean atmosphere (e.g. offices, shops, schools, hotels).
C2
low
Atmospheres with low level of pollution. Mostly rural areas. Unheated premises, where condensation may occur (e.g. depots, sports halls).
C3
medium
Urban or industrial atmosphere, moderate sulphur dioxide pollution. Coastal areas with low salinity.Industrial premises with high humidity and some air pollution (e.g. food-processing plants, laundries, breweries and dairies).
C4
high
Industrial and coastal areas with moderate salinity.Chemical plants, swimming-pools, ship- and boatyards.

C5-I
very high (industrial)

Industrial areas with high humidity and aggressive atmosphere. Buildings or zones with almost permanent condensation and high level of pollution.

С5-М
very high (marine)

Coastal and offshore areas with high salinity.Premises and areas with virtually constant humidity and high level of pollution.
Useful life of buildings

 

Polymer coating must have durable technical properties and appearance, which have to be preserved throughout the whole period of operation of an object with minimum maintenance costs. The reference useful lives for various types of buildings are determined in DBN V.1.2-14:2018.

 

In most cases, the planned useful life of a building comprises over 50 years. Such durability of roof and façade solutions is achieved due to application of the most resistant coatings – Hiarc, Hiarc Max, and Pural. The useful life of agricultural and other buildings with short operation period comprises from 15 to 50 years, thus a broader range of coatings is suitable for them.

 

The reference planned useful lives of buildings are taken according to DBN V.1.2-14:2018

Building typeIndicative useful life, years
Residential and public100
Industrial and ancillary60
Warehouses60
Agricultural50
Mobile dismountable (including industrial, residential etc.)20
Mobile container buildings15

 

Special requirements to coating of steel construction materials

 

Roofs

 

Roofs are exposed to stronger UV irradiation, compared to other surfaces of the building. Snow, stagnant water, and accumulated trash create load onto the roof, which requires highly corrosion-resistant coatings.

 

The surface is deteriorated due to snow, ice, and movement of people on the roof. This causes increased requirements to coatings resistant to wear. Apart from that, coating of roofs connected with rebates, has to withstand shaping, carried out using manual tools.

 

Façades

 

Ventilated façades and sandwich panels have to preserve attractive appearance, therefore it is important that the polymer coating ensures resistance to UV irradiation, is easy to clean or self-cleaning. In certain cases, good resistance to wear is required.

 

Water drainage systems

 

Water drainage gullies have to have good corrosion resistance, because stagnant water and trash are accumulated there, and stormwater drainage pipes – good resistance to scratching. In such a case, a steel sheet has to be painted from both sides and be suitable for shaping.

 

Ceilings and walls

 

Cleanliness and possibility to clean are the most important parameters for internal surfaces of buildings.

 

Properties and selection criteria of polymer coatings

 

Applicability and resistance of coatings in various atmospheric conditions are influenced by a number of factors, such as coating thickness, paint type, and usage of admixtures (pigments, stabilizing agents). Coating thickness affects mainly the mechanical properties: shaping, resistance to wear and corrosion, scratching resistance.

 

Hiarc and Hiarc Max have the best temperature and chemical resistance, as well as high UV resistance. Application of such coatings allows a façade to preserve its saturated colour and shine throughout a long period under the influence of solar irradiation. Excellent properties of such coatings are based on molecular build-up, and the non-organic pigmentation gives wonderful stability to a colour shade. The Hiarc Max coating has a thicker primer layer, compared to the standard Hiarc coating (20 mcm/7mcm) with an anti-corrosion pigment, and thus it is suitable for more responsible conditions of application. Hiarc is the best choice for façades.

 

Pural and Pural Matt are polyurethane-based coatings specially designed for roofs. Their non-organic pigmentation and chemical composition guarantee the highest corrosion resistance in case of influence of non-organic pollutants (salts, acids, alkali), very good resistance towards UV irradiation, as well as heat and colour stability. The thick Plural coating has excellent shaping capacity. Polyamide is used in such coating, enabling scratch resistance and improved bendability. Pural coatings are the best option for roofs and façades of industrial buildings.

 

Pural farm (Csafe) is a thick polyurethane-based coating, combining high durability, corrosion and scratch resistance. Pural farm is easily processed and can be bent without any restrictions on the bending radius. The chemical composition of the coating ensures the best corrosion stability towards organic corrosive pollutants, including those from the animal farming industry (salts of phosphorus acid and deactivating agents). A product with such coating is highly durable against considerable mechanical loads onto the roof. Pural farm has high self-cleaning capacity and is designed for objects with increased humidity, which are subject to frequent cleaning.

 

Polyester and Polyester Matt coatings have medium resistance to weather conditions and mechanical resistance. Apart from mechanical and corrosion resistance, Polyester Matt has a thicker layer than the standard Polyester coating. Moreover, the matt coating does not contain matting substances, like in the smooth Polyester coating. Due to low price, such coatings are recommended for roofs and walls of buildings with short useful life, as well as in internal dry premises.

 

FoodSafe film laminate has high shaping capacity and durability against organic substances. As a rule, this coating has smooth white surface. FoodSafe is non-toxic, resistant to washing and cleaning agents, easy to clean, and does not absorb water. This coating was thoroughly tested for compliance with the strict requirements of the HACCP food safety standard. Food can even be in direct contact with the FoodSafe laminate – it is the best solution for interior usage at food (in refrigerator and freezer chambers) and pharmaceutical industry facilities, as well as in premises with increased humidity.

 

Coating PropertyCoating
HiarcHiarc MaxPuralPural MattPural farm (Csafe)PolyesterPolyester MattLaminate FoodSafe

Coating thickness, µm

274050502002535120
Surface texturesmoothsmoothslightly granularmattslightly granularsmoothgranularsmooth
Gloss class, Gardner 60°, EN 10169-130-4030-4034-46<54030-40<57-13
Shaping (bending) capacitygoodgoodgoodgoodgoodsatisfactorysatisfactorygood
Min. bending radius (placticity)1t*1t1t1t1t3t2t1t
Min. shaping temperature, °C-10-10-15-15+1500+10
Max. ambient temperature, °C110110100100100909060
Class of reaction to fire, DSTU EN 13501-1:2016A1 s1, d0A1 s1, d0A2 s2, d0A2 s2, d0C-s2, d1A1A2 s1, d0
Class of UV irradiation resistanceRuv4Ruv4Ruv4Ruv4Ruv4Ruv2Ruv3
Class of corrosion resistanceRC4RC5RC5RC5RC4RC3RC4RC5
Scratch resistance30N35N40N40N35N20N25N55N
Pollution resistanceexcellentexcellentvery goodvery goodexcellentsatisfactorygoodexcellent

* sheet thickness

 

Coating resistance to natural UV irradiation is indicated in the Ruv1-Ruv4 categories in accordance with EN10169. UV resistance shows how well a coating can preserve its original colour and gloss level in case of exterior usage. Coatings of the Ruv1 category have very weak resistance to UV irradiation and are to be used only in the interior of premises. Ruv4 coatings have high UV resistance and are therefore recommended for exterior usage.

 

Recommendations on usage of coatings

 

A suitable coating can be selected for virtually any construction object, considering the ambient conditions, planned useful life, and special requirements.

 

Usage of Ruukki polymer coatings for roofs (R) and façades (F)

Warranty for aesthetic properties of productsCorrosion resistance category, DSTU ISO 12944-2:2019HiarcHiarc MaxPuralPural MattPural farm (Csafe)PolyesterPolyester Matt
RFRFRFRFRFRFRF
Standard warranty, yearsС2 20 20202020 1515101010 
С3 20 20202020 1515101010 
Special warranty, yearsС4   10*10*10*10*       
С5-I/M   1-5*1-5*1-5*1-5*       

 

Usage of Ruukki polymer coatings for interior premises (ceilings and partitions)

Load categoryHiarcHiarc MaxPuralPural MattPural farm (Csafe)PolyesterPolyester MattLaminate FoodSafe
C1
C2
C3
C4 ✔*✔*   ✔*
С5-I/M ✔*      

* The conditions of the C4 and C5-I/M impact categories are very hard, thus only a limited warranty can be given for a specific project.

Unpainted galvanized steel sheets are recommended for the conditions not higher than C2.

The recommendations in the tables are presented for steels with 275 g/m2 galvanization degree.

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