Pre-painted steel coils——SMP coating type instruction

Pre-painted steel coils——SMP coating type instruction

SMP coating type:

1,Instruction:

SMP coating is shorted for Silicone Mobified Polyester coating.Since the polyester contains an active group -OH/-COOH, it is easily reacted with other macromolecular substances. The modified PE is resistant to sunlight and powdering, and is denatured by a Silicone resin having excellent color retention and heat resistance.

2,Life span:

Compare to PE coating,the denaturation ratio is between 5% and 50%.SMP provides better durability for steel sheetsand the corrosion resistance can last for 10-12 years. Of course, the price is higher than PE coating, but because the material is made of Silicone resin,the adhesion and formability are not ideal.SMP color coated steel sheets are not suitable for applications where multiple molding processes are required,and most of them are used for roofs and exterior walls of buildings.

Coating structure details:

3,Substrate:

PhuizerColor SP-20:Hot dipped galvanized steel coils,according to JIS G3302,Zinc coating 275 g/m²；

ColorFan SP-20F:Hot dipped galvalume(5% aluminum coating added in),according to JISG3317,Zinc coating: 275 g/m²;

ColorLume SP-20L:Hop dipped galvalume(55% aluminum coating added in ),according to JIS G3321,AZ coating:150 g/m²,standard thickness:0.576mm,other thickness could follow customers’ requirement.

Coating system:

Coating system with double-sided two-coating.

4,Pre-treatment:

According to different production line equipment,the Bonderite surface treatment agent produced by Chemetall S.A. of France is appropriately selected to form a surface-formed film with excellent density and excellent corrosion resistance on the surface of the coating.

Primer coating:

Using highly corrosion resistant Polyurethane(Also called PU),film thickness:5μm.

Top coating:

Using highly corrosion resistant SMP coating,film thickness 20-22μm.

Top coating color & gloss:

Color could be customized;

Top coating gloss is typically 25%(60° reflection angle,according to ASTM D523)

Back primer coating:

Using highly corrosion resistant Polyurethane(Also called PU),film thickness:2μm.

Back coating:

Using good corrosion resistant epoxy resin coating,polyester resin coating,film thickness:7-10μm.

Back coating color & gloss:

Back coating color is usually using beige,grey or white grey color.Back coating gloss is typically 25%(60° reflection angle,according to ASTM D523).

Strippable film:

We could add one layer of strippable film on the top coating,in order to reduce steel coils’ damage,when goods delivery,storage and processing.This strippable film need to be ripped off within one month after installation.And please rip off this film within 5 months,to avoid difficult to peel off  the film,when steel coils are only under storage.

Performance:

5,Typical properties:

●Pencil hardness( ASTM D3363):2H/3H

●Impact test(ASTM D2794):The impact was made by a 12.7 mm diameter impact head, and used 500g heavy hammer to impact at 50cm height, and then quickly peel off at a 180°angle with 3M #600 tape, and the painting film adhered well without any peeling.

●Erichsen test(ASTM E643):At speed 12±6mm/min to do 7mm stroke after molding,and then quickly peel off at a 180°angle with 3M #600 tape, and the painting film adhered well without any peeling.

●Bending test(ASTM D4145):Cut sample and make it under 180° angle,then make the inner diameter of the curved arc 3 times the thickness value (3T),and then quickly peel off at a 180°angle with 3M #600 tape, and the painting film adhered well without any peeling.

●Solvent resistance(ASTM D5402):Using gauze which is dipped with M.E.K. or toluene,and wipe back and forth 100 times on sample surface with 1KG strength,and no substrate was showing.

6,Accelerated corrosion and weathering test:

●Salt spray test(ASTM B117):After 1000 hours’ salt spray test,there is no any red rust, foaming (above 6F), and corrosion of the coating happening part 5mm away from the score(Un-scribed area).

Note:This is for top coating,for back coating is 150hours.

●Weathering Test-QUV(ASTM G53):After 1000hours,there is no significant color change or chalking.

●Humidity resistance test(ASTM D2247):No any significant changes after 1000 hours of humidity test(98% humidity).

●Chemical resistance-spot test(ASTM D1308):No any significant changes after 24hours with 5%H2SO4 on surface;No any significant changes after 24hours with 5%NaOH on surface.

7,Handling and forming:

In order to avoid damage to the surface of the product, the product must be handled carefully during handling, transportation, molding and installation. Improper use of molding lubricants will affect product characteristics and cause surface contamination. Do not use if not necessary.

8,Storage:

In any case, the steel coils should never be stored or stored in a damp environment.Because the action of the capillary will suck moisture into the surface of steel coil, moisture gas or water will not evaporate normally, which may lead to deterioration of product characteristics, shorten the expected service life, and affect the appearance of the product. The storage for related products,such as color corrugated steel sheets,sandwich panels,etc.,also requires special attention to this problem.