Hot-dip galvanized steel sheet

Cr-free passivation hot-dip galvanized steel sheet is designed toretard corrosion by an organic composite film with an advancedbarrier property and an inorganic rust-preventive additive witha self-healing property in the organic film, replacing traditionalchromate conversion coating. lt is widely used as a low-costrust-preventive process for suppressing white rust of Zn.

Cr-free anti-fingerprinting hot-dip galvanized steel sheet isa high added-value product with organic resin coating film(no-chromate absolutely) on the substrate, has good multipefunctions including corrosion resistance, anti-fingerprintingproperty,electrical conductivity(grounding property) andpaintability.

Above-mention product is applied to high grade c omputercabinet casing, the chassis and bottom plates of OA and AVequipment,internal plates of home appliances and similarproducts.

Electro-galvanized steel sheet

55% Al-Zn alloy galvanized steel sheet

55% Al-Zn alloy coated steel sheet has excellent weatherproof property and appearance. In addition to the plate for top grade building outside, the volume of 55% Al-Zn alloy coated sheet with Cr-free passivation and anti-fingerprinting treatment used in home appliaance is getting bigger and bigger.

Cr-free passivation and anti-fingerprinting 55% Al-Zn alloy coated sheet are applicable to rear back panel for refrigerator and air conditioner or ther internal structural parts. This kind of product has even beautiful spangle, with excellent corrosion resistance property and good adhesion with foaming adhesive.

Specially used in explosion-proof band for CRT, the Crfree passivation 55% Al-Zn alloy coated sheet has excellent corrosion resistance property, weldability, heat resistance property. It is suitable for current process of CRT.

Features of prepainted steel

Process of corrosion of the prepainted steel sheet
The organic coating on surface of the prepainted steel sheet can prevent the base metal coated with the coating from being quickly corroded. And the coated base metal selected for the prepainted steel sheet also possess corresponding resistance to corrosion.

So, the resistance to corrosion of the prepainted steel sheet mainly includes two parts, namely the resistance of the base metal and the resistance to deterioration of the coating film.

Under normal circumstances, the process of deterioration often starts from a loss of gloss, and then the chalking and shedding of the membrane. Owing to the decomposition of the resin content, the surface of the coating membrane starts chalking and then shedding.

Process of Deterioration
Lost of gloss→fading → chalking→ surface rupture→ foaming and shedding of the coating membrane→ white/red rust Apperance of Deterioration: shown in the following table:

1. Acid/alkaline-resistance test
Principle
Soak the sample in the acid/alkaline solution with a specified concentration for a certain period, and then take it out of the solution to assess the change of color and gloss, and whether it foams, sheds, etc.

Result
According to the standard GB/T 1766, assess the grade of the sample in loss of gloss, color change, foaming and shedding, etc.
In normal conditions, the iron is apt to rust, however, once the iron is galvanized, it will have a quite good resistance to corrosion and won’t rust. For details, please refer to the test below.

2. Salt fog test

Principle
After expose the sample in the neutral Nacl mist for a specified time, assess the surface foaming and rusting, the outreach of surface corrosion, etc.

Result
1.For the flat-sheet sample, assess the grade of foaming and rusting by the GB/T 1766 standard, and take the worst result as the final.

2.For the scratched or notched sample, choose a typical area within the lineation scope, measure the intervals between the maximum outreach of corrosion of the foamed and rusted part and the lineation at six equidistant points at least, and then take the arithmetic mean value, namely the outreach of corrosion on average, and record the maximum and minimum distances at the same time.<0}(Histogram of the test of resistance to neutral salt mist).

Introduction of the feature

All the iron and steel pieces will never escape the possibility of corrosion, decaying, even loss of original mechanical strength on the account of contact with and penetration of corrosive media in the air (O2, H2O, Cl etc. contained in the air). To inhibit the corrosion from occurring as long as possible, the approach that is frequently resorted to is applying organic coating on the surface to serve as a physical protection, by isolating it from the corrosive media.

Coating treatment with organic coating is such that the cold-assteel and monotonous appearance of the steel sheet can be remade thoroughly. The organic coating beautifies the steel sheet with different color and amplifies its sense of quality, meeting the aesthetical requirement.

There are two types of degreasing process in popular use-water-borne alkaline degreasing and organic solvent degreasing

The detergent will react with the rust preventive oil on the steel sheet surface, physically and chemically, by way of spraying, brushing, dipping or in electrolytic manner etc. to remove the preventive oil and such impurities as residual carbon, iron powder and so on absorbed in the process of production.

The common detergent is made of NaOH, Na2CO3, Na3PO4 and other alkali metal salts in a proportion to the compound surface active agent, then solved in water. Where the galvanized sheet or anti-fingerprint sheet is treated, consideration shall be taken into the alkali resistance of the galvanizing coating and of the organic film, and the alkalinity of detergent ought to be properly reduced.

The detergent reacts with oil film by means of penetration, soaking, emulsion and separation, to emulsify the oil into milklike compound - emulsion, which carries with it the impurities such as powdery carbon, iron etc. departing off the sheet and is discharged into degreasing solution. Thus doing the end is served of oil removal and cleaning.

It is to place the oil-contained metal pieces in the vapor composed of trichloro-ethane and trichlorethylene etc. to take the oil film off the metal surface.

As a result of dissolution and dilution to rust preventive oil by organic solvent, the oil viscosity ever high will be reduced to a very low degree whereby oil slackens off the metal surface, then is washed away with the solution carrying it.

Ultrasonic cleaning is frequently adopted to enhance the dissolution effect.

When the electro-galvanized / hot-dip galvanized antifingerprinting steel surface slightly soiled, it can take a dip ethanol or acetone soft cloth to wipe the plate, so as to achieve decontamination cleansing effect.

Phosphating treatment is to place the metal to be treated into the phosphating solution where a layer of compact chemical conversion film is formed on the surface of metal reacting with dihydrogen phosphate in the phosphating solution, which serves as pre-chemical treatment of organic coating.

The treatment is usually spraying or dipping. Phosphating of steel for appliance is adopting much more frequently the pseudo-conversion phosphating than the conversion phosphating (the latter applicable only to the cold rolled sheet). The former is featured as one with good adhesion and corrosion-resistance while the latter is of better workability and shorter handling time, suitable for fast streamline production.

Phosphating can inhibit the activity of metal surface to a minimum possible degree and minimize the subsequent corrosion action to a lowest possible level.

Phosphating film creates a “rough face” to the metal, providing a good bonding interface for paint or other organic coating and resultantly reinforcing the adhesion.

Equipotential and insulation with respect to phosphating film deter the corrosive creepage under the film of organic coating.

After coating the galvanized steel sheet has excellent resistance-to-punching corrosion by the reason of sacrificial protective action. The cold rolled sheet, due to the fact that Fe is contained in the phosphating film of it therefore capable of forming Me2Fe (PO4)2·4H2O crystal excellent in alkaliresistance, is outperforming in preventing the corrosive propagation under film

The most popular coating technology in the household appliance manufacturing industry is electrostatic powder coating process. It is to apply induction, by means of induction effect of high-voltage electric field, on powder coating and the target part, so loaded with the opposite electric charge that the powder coating is absorbed onto the target part. The target parts will then be put in the baking oven for baking to flow flat into film.

The powder coating is classified into two: thermoplastic type and thermosetting type. The former is made simply by its fusion to flow flat; the latter, after flow flat, still need cross-linking hardening to form film.

It can be applied directly onto the target parts after its surface treatment;
It is applicable where the coating thickness is between 50-50μm, and is of uniform thickness, no flowing mark.

It is widely applicable to the different target parts, can be used on target part in different size and different shape, including inner and outer wall of the pipe.

It is flexibly adaptable to various kinds of powder coating; the spilt powder coating can be reclaimed for use. Its utilization efficiency therefore is high.

In a trication Zinc based phosphating system for general pseudo-conversion phosphating and under normal process conditions, the cold rolled sheet, galvanized sheet and galvannealed sheet are exclusively of excellent phosphatibility, the phosphating film is compactly crystallined and weighed as to be ranging in 2-4g/m2.

Cold rolled sheet for side cover of refrigerator	Electro-galvanized sheet for casing of the washing machine	Hot-dip galvanized sheet for outdoor mounted set for air conditioner	Galvannealed sheet for outdoor mounted set for air conditioner

Environmental Product Declaration

Drawing 1 shows contributions relevant to all phases of cold-rolled product life cycle, cold-rolled product life cycle process is divided into three phases

of steel manufacture process, transportation, upstream according to environmental influence kind.

● Steel manufacture process" mainly refers to production process in steel enterprise;

● Transportation" mainly refers to the transportation process from producing area to steel enterprise of bulk original materials, energies, auxiliary materials such as iron ore, coal, limestone;

● Upstream" mainly refers to mining, production process of raw materials, energy, auxiliary materials procured externally for steel enterprise production outside steel enterprise , including environmental gains generated by auxiliary steel product outside the enterprise, such as cement raw materials used for blast furnace slag.

In all phases of cold-rolled product life cycle, 94% of ADP, 77% of EDP occur in steel manufacture process. They are mainly depletion of iron ore resource, coal in steel manufacture process.

81% of GHG is generated in steel production process, in which 10% generated in transportation phase, 8% coming from raw material and energy of upstream. In steel production, the coal as main energy source and reducing agent is the most important source of GHG generated.

Influence to AP and EP is mainly generated in transportation phase, for raw materials, energy sources of iron ore, coal etc. coming from Australia, South America, due to large transport amount, far transport distance, seagoing vessel is adopted for transportation with main fuel of diesel oil, therefore sulfur dioxide, nitrogen dioxide generated during transportation cause more serious influence to AP, EP. Removal device of sulfur dioxide, nitrogen dioxide is set in iron and steel manufacture process to reduce environmental influence at maximum.

6.1 Cycle>
All iron and steel products are valuable recyclable materials 100% of which can be reclaimed and utilized, Baosteel uses recycled steel scrap as raw material of steelmaking; all wrappage can be recycled and utilized, such as steel binding band, steel angle armor, covering plate, wrapper sheet of internal and external wrapper sheet, wooden bracket, antirust paper etc. can be recycled and utilized. Environmental influence of iron and steel products supplied by Baosteel has contained environmental benefit brought by reclamation of steel material after use.

6.2 Final disposal
100% of iron and steel product can be recycled without any waste treatment (such as burning, burying etc.), 100% of slitter edge and cuttings generated during iron and steel product processing can be recycled and utilized.

Drawing 1 shows contributions relevant to all phases of hot-dip galvanized product life cycle, hot-dip galvanized product life cycle process is

divided into three phases of steel manufacture process, transportation, upstream according to environmental influence kind.
● "Steel manufacture process" mainly refers to production process in steel enterprise;
● "Transportation" mainly refers to the transportation process from producing area to steel enterprise of bulk original materials, energies, auxiliary materials such as iron ore, coal, limestone;
● "Upstream" mainly refers to mining, production process of raw materials, energy, auxiliary materials procured externally for steel enterprise production outside steel enterprise , including environmental gains generated by auxiliary steel product outside the enterprise, such as cement raw materials used for blast furnace slag.


Throughout all phases of hot-dip galvanized product life cycle, 91% of ADP, 73% of EDP occur in steel manufacture process. They are mainly depletion of iron ore resource, coal in steel manufacture process.

78% of GHG is generated in steel production process, in which 10% generated in transportation phase, 12% coming from raw material and energy of upstream. In steel production, the coal as main energy source and reducing agent is the most important source of GHG generated.

Influence to AP and EP is mainly generated in transportation phase, for raw materials, energy sources of iron ore, coal etc. coming from Australia, South America, due to large transport amount, far transport distance, seagoing vessel is adopted for transportation with main fuel of diesel oil, therefore sulfur dioxide, nitrogen dioxide generated during transportation cause more serious influence to AP, EP. Removal device of sulfur dioxide, nitrogen dioxide is set in iron and steel manufacture process to reduce environmental influence at the maximum.

6.1 Cycle
All iron and steel products are valuable recyclable materials 100% of which can be reclaimed and utilized, Baosteel uses recycled steel scrap as raw material of steelmaking; all wrappage can be recycled and utilized, such as steel binding band, steel angle armor, covering plate, wrapper sheet of internal and external wrapper sheet, wooden bracket, antirust paper etc. can be recycled and utilized. Environmental influence of iron and steel products supplied by Baosteel has contained environmental benefit brought by reclamation of steel material after use.

6.2 Final disposal
100% of iron and steel product can be recycled without any waste treatment (such as burning, burying etc.), 100% of slitter edge and cuttings generated during iron and steel product processing can be recycled and utilized

Throughout all phases of electro-galvanized product life cycle, 93% of ADP, 78% of EDP occur in steel manufacture process. They are mainly depletion of iron ore resource, coal in steel manufacture process.

83% of GHG is generated in steel production process, in which 9% generated in transportation phase, 8% coming from raw material and energy of upstream. In steel production, the coal as main energy source and reducing agent is the most important source of GHG generated.

Influence to AP and EP is mainly generated in transportation phase, for raw materials, energy sources of iron ore, coal etc. coming from Australia, South America, due to large transport amount, far transport distance, seagoing vessel is adopted for transportation with main fuel of diesel oil, therefore sulfur dioxide, nitrogen dioxide generated during transportation cause more serious influence to AP, EP. Removal device of sulfur dioxide, nitrogen dioxide is set in iron and steel manufacture process to reduce environmental influence at the maximum.

6.1 Cycle
All iron and steel products are valuable recyclable materials 100% of which can be reclaimed and utilized, Baosteel uses recycled steel scrap as raw material of steelmaking; all wrappage can be recycled and utilized, such as steel binding band, steel angle armor, covering plate, wrapper sheet of internal and external wrapper sheet, wooden bracket, antirust paper etc. can be recycled and utilized. Environmental influence of iron and steel products supplied by Baosteel has contained environmental benefit brought by reclamation of steel material after use.

6.2 Final disposal
100% of iron and steel product can be recycled without any waste treatment (such as burning, burying etc.), 100% of slitter edge and cuttings generated during iron and steel product processing can be recycled and utilized.