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Introduction Of Home Appliance Sheet Processing And Coating Process

May 6, 2022

Except For Color-Coated Sheets, All The Outer Covering Parts Of Household Appliances Need To Be Painted Before They Are Made Into Finished Products, So As To Improve The Service Life And Decorative Properties Of Steel Parts In Household Appliances.

 

Improve The Service Life Of Steel Parts In Home Appliances

All Steel Parts Are Rusted And Rotted In The Air Due To Contact And Penetration With Corrosive Media (O2, H2O, CI, Etc. In The Air) Until They Lose Their Original Mechanical Strength. In Order To Delay The Occurrence Of Corrosion, The Most Common Method Is To Apply An Organic Coating On The Surface Of The Steel Parts To Isolate The Steel Parts From The Corrosive Medium And Play A Role In Physical Protection.

 

Decorative

Through The Application Of Organic Coating, The Cold And Monotonous Appearance Of The Steel Plate Can Be Completely Changed. The Organic Coating Can Endow The Steel Plate With Various Colors And Textures To Meet The Aesthetic Requirements.

 

Home Appliance Sheet Processing Process

The Conventional Processing Process Of Home Appliance Steel Parts Is As Follows:

 

Shearing - Stamping - Degreasing - Rinsing - Surface Conditioning - Phosphating - Rinsing - Passivation (Sealing) - Drying - Powder Coating - Baking And Curing

 

Degreasing Process

 

There Are Two Commonly Used Degreasing Processes: Alkaline Water-Based Degreasing And Organic Solvent Degreasing.

Alkaline Water Agent Degreasing: The Alkaline Chemical Degreasing Agent Is In Contact With The Anti-Rust Oil Film On The Surface

Of The Steel Plate By Spraying, Brushing, Dipping, Electrolysis, Etc. And Has A Physical And Chemical Reaction To Remove The

Anti-Rust Oil Film And The Carbon Residue Adsorbed During The Production Process Of The Steel Plate. , Iron Powder And Other

Foreign Objects Are Removed.

Commonly Used Alkaline Degreasing Agents Are Made By Dissolving Alkali Metal Salts Such As NaOH, Na2CO3, Na3PO4

And Other Compound Surfactants In Water In Proportion; And The Alkali Resistance Of The Organic Film, The Alkalinity Of The Degreaser

Should Be Moderately Reduced. When Working, The Oil Is Emulsified Into A Milk-Like Mixture-Emulsion Through The Penetration, Infiltration,

Emulsification And Dispersion Of The Oil Film, And Wraps Impurities Such As Carbon Powder And Iron Powder, And Leaves The Steel Plate And

Enters The Degreasing Solution To Achieve Degreasing And Cleaning.

Organic Solvent Degreasing: The Oily Metal Workpiece Is Placed In The Steam Of Trichloroethane, Trichloroethylene, Etc. To Remove The Oil Film From The Metal Surface. By Dissolving And Diluting The Rust Preventive Oil With Organic Solvents, The Oil With High Viscosity Is Reduced To A Very Low Viscosity, So That The Oil And The Metal Surface Are Loosened, And Then Washed Away By The Solvent Surrounding It. In Order To Strengthen The Dissolution Effect, Ultrasonic Cleaning Is Often Supplemented. When The Surface Of Electro-Galvanized/Hot-Dip Galvanized Fingerprint-Resistant Steel Plate Is Slightly Stained, It Can Be Wiped With A Clean Soft Cloth Dipped In Ethanol Or Propanol To Achieve The Effect Of Decontamination And Cleaning.

 

Phosphating Process And Basic Principle

Phosphating Treatment Is To Place The Metal To Be Treated In A Phosphating Solution, And A Dense Chemical Conversion Film Is Formed On The Surface Through The Reaction Of Dihydrogen Phosphate And The Metal In The Phosphating Solution As A Chemical Pretreatment For Spraying Organic Coatings. The Treatment Method Is Usually Spraying Or Dipping.

The Phosphating Of Household Appliances Is Mainly Based On Pseudo-Conversion Type Phosphating, And A Very Small Amount Of Conversion Type Phosphating Is Used (Only Applicable To Cold-Rolled Sheets). The Former Has Good Adhesion And Corrosion Resistance, While The Latter Has Better Processability And Shorter Processing Time, And Is Suitable For Fast Assembly Lines.

Phosphating Can Convert The Activity Of The Metal Surface To A Minimum, And Reduce The Subsequent Corrosion Reaction To A Minimum.

Phosphating Films Can Provide A "Rough Surface" To The Metal, Providing A Good Bite To Paint Or Other Organic Films And Enhancing Their Adhesion. The Equipotential And Insulating Properties Of The Phosphide Film Inhibit The Under-Film Corrosion Propagation Of The Organic Coating.

Galvanized Steel Sheet Has Good Anti-Perforation Corrosion Performance Due To The Sacrificial Anode Protection Of Zinc Layer After Coating. Cold-Rolled Sheet Can Form Me2Fe(PO4)2·4H2O Crystals With Excellent Alkali Resistance Due To The Fe Content In The Phosphating Film. There Is Thus An Advantage In Preventing The Propagation Of Corrosion Under The Film.

 

Common Spraying Processes And Basic Principles

The Most Commonly Used Spraying Process In Home Appliance Manufacturing Is Electrostatic Powder Coating. The Electrostatic Powder Coating Method Uses The Induction Effect Of High-Voltage Electric Field, So That The Powder Coating And The Object To Be Coated Are Induced And Charged With Opposite Charges Respectively, And The Powder Coating Is Adsorbed To The Object To Be Coated, And Then The Object To Be Coated Is Placed In A Baking Oven For Drying. Baked Leveling Film. Thermoplastic Powder Coatings Only Need To Be Melted And Leveled, While Thermosetting Powder Coatings Need To Be Cross-Linked And Cured To Form A Film After Leveling.

 

 

Advantages Of Electrostatic Powder Coating

The Surface Of The Coated Object Can Be Sprayed Directly; It Is Suitable For The Coating Film With A Thickness Of 50-150 Μm, The Thickness Of The Coating Film Is Uniform, And It Is Not Easy To Sag; It Has Strong Adaptability To The Coated Object And Can Be Sprayed With Different Sizes And Shapes Of The Coated Object , Including The Inner And Outer Walls Of The Pipeline; Strong Adaptability To Various Powder Coatings, The Spilled Powder Coatings Can Be Recycled, And The Utilization Rate Of The Coatings Is High.