Polymer Coated Steel

Polymer Coated Steel

Galvanized steel with polymer coating is today extremely popular in the world markets, the demand for this type of metal products is growing every year, production is developing rapidly.

Product Highlights

Polymer-coated materials combine the strength and formability of steel with the corrosion resistance of zinc and paint. The result is a finished material with a beautiful appearance. Coatings can be of different colors and shades and, accordingly, have different properties.

Painted rolled products are manufactured with one-, two-layer coatings up to 200 microns thick. Possible coating options: with one-sided coating, two-sided identical coating on both sides and two-sided different coating of the front and back sides.

Rental is transported by all means of transport in accordance with the rules for the carriage of goods operating on a particular type of transport.

The packaging of rolled products with a polymer coating should protect from moisture on the ends of packs and rolls and in the inter-turn space of rolls, as well as protect rolls and packs from mechanical damage during their transportation.

Each roll (pack) is provided with a packing label or tag indicating the name and / or trademark of the manufacturer, batch number, production date, steel grade, geometric dimensions of the polymer-coated steel and color of coating, net weight, strip length per roll or quantity sheets in a pack.

The main dimensional characteristics of rolled steel with a polymer coating

Metric

Value range

Thickness from 0.2 to 1.2 for a cold-rolled base

from 0.4 to 1.2 for hot-dip galv anized basics

Width 700-1650
Roll Diameter inner: 508; 610 + 20

outdoor: 950-2200

Roll weight 5-15 t

Polymer coated

The main advantages of polymer coated steel are as follows:

1. Operational

  • The possibility of processing metal with a polymer coating into finished products (metal siding, profiled flooring, and so on)
  • Uniform coating thickness and uniform properties over the entire surface
  • Almost complete absence of pores and, accordingly, better protective properties
  • High adhesion
  • Weather resistance
  • Preservation of protective and decorative properties for more than 10 years

2. Economic

Polymer coating lines provide high performance and quality, reducing the cost of coating. The working speed of the lines is about 100 m / min.

For the end user, the transition from the use of metal for further painting to metal with a polymer coating already applied means that there is no need to invest in our own paint shop, degreasing unit, other equipment for surface cleaning, as well as in the subsequent processing of waste.

The use of polymer-coated coiled steel in the manufacturing process provides a significant reduction:

  • production costs;
  • energy costs;
  • production terms;
  • inventory financing costs (raw materials, chemicals and interim storage).

Types and classification of polymer coated steel

in appearance of the coating surface:

  • 1 class,
  • 2nd grade.

The front side of the polymer-coated steel is the side exposed to external influences.

Two-layer polymer coating – a coating consisting of a layer of soil and a layer of finishing enamel or plastisol.

A single-layer coating is a coating on the reverse side of a rolled product, consisting of a layer of protective enamel without regulatory requirements for appearance, corrosion resistance, etc.

Single-sided polymer-coated rolled products – rolled products with a two-layer polymer coating on the front side and a single-layer polymer coating on the reverse side.

In the production of this type of rolled products, various types of polymer coatings are used: polyester, plastisol, pural, polyvinylidene fluoride, etc. A detailed description of polymer coatings is given in the next part of the chapter.

The color scheme of the rental is most often determined by the RAL scale. The standard colors most commonly used for painting are the following:

  • RAL 9002 – white-gray
  • RAL 6003 – olive-green
  • RAL 9010 – Signal-White
  • RAL 6005 – Moss Green
  • RAL 1013 – white with a greenish-gray or yellowish-gray tint
  • RAL 5015 – sky blue
  • RAL 5010 – Blue Gentian
  • RAL 1015 – light ivory
  • RAL 7016 – Anthracite Gray
  • RAL 9006 – white aluminum
  • RAL 7016 – gray basalt
  • RAL 3009 – Oxide-Red
  • RAL 8017 – chocolate-gray
  • RAL 3000 – fire-red
  • RAL 5301 – taupe

Types polymer

General characteristics of polymer coating

A polymer coating is a material made from organic polymers (resins or plastics) with the addition of pigments, additives and solvents, forming a coating with protective properties. The polymer coating not only protects the metal from mechanical and climatic influences, but also gives the buildings an architectural and artistic expression.

The most important requirements for coatings are the strong adhesion (adhesion) of the individual layers to each other, the lower layer with the substrate, hardness, bending and impact strength, moisture resistance, weather resistance, a set of decorative properties (transparency or hiding power, color, gloss, pattern, etc. ) In the preparation of multilayer coatings, the following materials are used: primers, which are applied directly to the substrate for its anticorrosion protection and ensuring adhesion, paint, enamel.

In the production of pre-painted rolled products, various types of polymer coatings are used. Polyester coatings are most prevalent in European countries. There are two main types of paints for coloring metal coils: thermosetting and thermoplastic, which can be divided into 8 types, depending on the type of resin used:

  • alkyd coatings
  • acrylic coatings
  • epoxy coatings
  • polyester coatings
  • polyurethane coatings
  • silicone modified coatings
  • coatings based on PVC (polyvinyl chloride)
  • coatings based on fluoropolymers, for example PVDF (polyvinyl difluoride)

Below are the types and main characteristics of coatings.

Types of polymer coatings

Type and material
coverings

Character

Thickness range, µM

Typical thickness
coatings, µM

Paintwork (thickness coatings – from 5 to 60 microns depending from coating material)
Acrylic AY Speakers 5-25 25
Epoxy EP ES 3-20 Not installed
Polyester SP PL 5-60 25
Polyamide modified
polyester
SP-PA PLA 15-50 25
Silicone-modified
polyester
SP-SI PEJS 15-40 25
Acrylic Silicone AY-SI AS-WS 25 25
Polyurethane PUR UR 10-60 25
Polyamide modified
polyurethane
PUR-PA PAU 10-50 25
Polyvinylidene fluoride PVDF PVDF 20-60 25
Plastisol (thickness
coatings – from 40 to 200 microns)
Polyvinyl chloride plastisol
PVS (P) PVA (P) 40-200 100; 200

Comparative characteristics of polymer coatings

Coating Properties

Polyester

Matte Polyester

Plastisol

Pural

PVDF (PVF 2)

μm thickness

25

35

200

50

27

Corrosion resistance

good

good

low

good

great

Resistance to atmospheric
impacts

good

good

great

great

good

UV resistant
radiation

satisfactory

good

satisfactory

good

great

Resistance to mechanical
damage

medium

satisfactory

great

good

good

Preservation of appearance

medium

satisfactory

satisfactory

good

great

Corrosion resistance – Salt test hours – Water test, at least hours

500

1000

500

1000

1000

1000

1000

1000

1000

1000

Max. permissible temperature ° C

120

120

60

120

120

Min. permissible pace. processing ° C

– 10

– 10

+ 10

– 15

– 10

Min. bending radius (formability) *

3 x t (low)

4 x t (low)

0 x t (good)

1 x t (good)

1 x t (good)

* t – sheet thickness without polymer coating

Source: According to enterprises

1) Polyester (PE, SP) The most inexpensive and popular polymer on the market for polymer coatings for galvanized steel sheet, which gives painted steel good UV and corrosion resistance, is polyester (polyester). The material has a high level of flexibility and formability, suitable for any climatic conditions. Resistance to mechanical damage in this type of coating is lower than that of Pural and PVDF coatings. More resistant to mechanical stress polyester sprinkled with quartz sand, however, it is significantly more expensive. In addition, when transporting it, a number of problems arise related to the possibility of damage to the lower layer of metal sheets (quartz sand, like sandpaper, scratches the surfaces of overlying sheets in contact with it).

Most often, coatings based on saturated polyesters (SP, PL) are used. The basis of the coating is polyester paint, which has good color fastness. The indicator of heat resistance to sunlight up to +120 ° C, and the lower temperature limit of polyester is -60 ° C. The thickness of the polyester on painted steel reaches 25 microns.

2) Matte Polyester (PEMA) A 35 micron thick polyester coating with a matte finish. It is a polyester modified with teflon. The material has high color fastness due to the refractive index of sunlight, good corrosion and mechanical resistance, retains its properties in any climate. This material is suitable for those who care about the lack of gloss of the product.

3) Plastisol (PVC-200) This is a decorative polymer with the thickest coating (200 microns), consists of polyvinyl chloride (PVC) and plasticizers, has an embossed surface. At a cost – one of the most expensive coatings. Due to the large thickness of the coating, the material is one of the most resistant to mechanical damage. However, due to its low temperature resistance and low resistance to UV radiation (when heated by direct sunlight above +80 ° C, the material ages quickly), it is not recommended to use it in the southern regions. Choosing plastisol for use in hot regions, you should focus only on light colors. They better reflect light, less heat and burn out.

Having a large thickness, plastisol has a high corrosion resistance, which creates additional protection in a polluted environment. Its color fastness is significantly lower than polyester. With a thickness of 175 microns, plastisol coating is only smooth. A stamped pattern can be rolled onto a coating with a thickness of 200 μm, an embossed textured surface is given (in this case, the thickness of the coating layer is significantly reduced at the places of embossing).

4) PURAL (PURAL) Coating based on polyurethane modified with polyamide, has a silky-matte structural surface. This material is not afraid of large daily temperature differences (up to 120 ° C). The material has high chemical resistance and color fastness. Resistant to mechanical stress. However, compared with plastisol, pural is less resistant to plastic deformation. This type is more expensive than polyester, but today it is one of the most optimal coatings for a combination of high performance and price. The coating thickness is 50 μm.

5) PVDF Coating with a thickness of 27 microns, consists of 80% polyvinyl chloride and 20% acrylic. This durable coating, the most resistant to UV radiation, practically does not fade, has a beautiful shine, and has self-washing. One of the most resistant to mechanical damage, to the aggression of nature and to the rudeness of the installers. The glossy surface of PVDF can have a metallic shade in silver or copper tones. To give a metallic sheen, the standard PVDF coating is complemented by a layer of transparent varnish with metallic pigment. This is the most durable coating, it is used even in aggressive environments, such as the sea coast. Ideal for walls.

6) The acrylic polymer coating is a paint coat, which is extremely unstable, it is easy to damage during installation of the product. It has heat resistance up to +120 ° C, but fades in the sun for 5 years, in addition, it has medium resistance to corrosion and after 2-3 years of operation begins to peel off. Layer thickness 25 microns. The minimum processing temperature is -10 ° C. Foreign firms have abandoned its use since 1997. Only domestic materials with such a coating are found on sale, however, they are recommended to be used only for temporary structures.

Polymer coated steel tips

Examples of application of anti-corrosion coatings

Degree
aggressiveness of the environment

Type
coverings

Thickness
coatings, mm

soil

enamel

enamel reverse side

Slightly aggressive
Polyester 
Pural

6-10

6-10

22-25

50

9-12

9-12 

Medium aggressive
Pural 
PVDF

6-10

6-10

50

25-27

9-12

9-12

The above characteristics of coatings relate primarily to liquid materials for painting metal by the roll method, which is the most common and in demand. At the same time, polymeric materials are also widely used in powder coating of rolled metal products (powder coil coating). In the production of powder coatings, hydroxyl-functional saturated polyesters are most often used in combination with free polyisocyanate resins. Powdered materials based on a mixture of acidic polyester and epoxy resins are also often used.

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