--Core process
1. Pre-treatment: remove oil stains and rust on the surface of castings (can be cleaned with degreasing agent);
2. Shot blasting treatment: According to the material and requirements of the casting, select projectiles of appropriate specifications, adjust the shot blasting speed and angle, and impact the workpiece surface;
3. Post-processing: Clean the remaining projectiles and iron filings on the surface of the workpiece, and dry it if necessary.
--Main function
• Surface cleaning: Completely remove scale, rust, old coatings and welding slag, suitable for blank cleaning of castings and forgings;
• Strengthen the surface: cause plastic deformation on the metal surface to form a dense hardened layer, improving the fatigue strength and corrosion resistance of the workpiece;
• Adjust roughness: Provide uniform surface roughness for subsequent spraying, electroplating and other processes to enhance coating adhesion.

--Core process
1. Pre-treatment: Clean the oil dirt and impurities on the surface of the casting to ensure the surface is dry;
2. Sandblasting treatment: Select abrasives according to the purpose of the casting (such as glass beads for stainless steel parts, quartz sand for cast iron parts), adjust the sandblasting pressure (generally 0.4-0.8MPa), and spray the surface of the workpiece;
3. Post-processing: Clean the residual abrasive on the surface and perform anti-rust treatment if necessary.
--Main function
• Casting surface cleaning: remove tiny rust, scale and burrs, suitable for surface treatment of precision parts;
• Beautify the surface: Make the surface of the workpiece a uniform matte or frosted texture to enhance the appearance;
• Improve performance: used for pretreatment for electroplating, refining metal surface grains, eliminating surface stress, and providing a good bonding surface for subsequent coatings (such as painting and electroplating).
• Used for precision castings: cleaning of thin-walled parts or complex structural parts to avoid mechanical damage.
• Welding and defect repair, cleaning weld areas to identify cracks or pores
• Remove surface impurities before repair.

--Core process
1. Pretreatment: degreasing (removing oil stains) → alkali washing (removing scale) → neutralization (removing residual alkali) → cleaning;
2. Anodizing: Use the aluminum part as the anode and the lead plate as the cathode, put it in an electrolyte such as sulfuric acid or oxalic acid and energize it, and control the voltage, current (DC, 12-20V) and time to form a porous oxide film;
--Main function

• Improve corrosion resistance: The oxide film is dense and non-conductive, which can effectively isolate air and moisture and protect the aluminum matrix from corrosion;
• Improve wear resistance: The oxide film has high hardness, which can improve the scratch resistance and wear resistance of the workpiece surface, and can also be used as a coating base layer to enhance adhesion.

--Core process
1. Pre-treatment: degreasing → rust removal (shot blasting or sand blasting) → phosphating (enhancing coating adhesion) → drying;
2. Electrostatic spraying: Spray the powder coating through a spray gun. The spray gun generates high-voltage static electricity, which makes the powder negatively charged and adsorbed to the surface of the grounded workpiece;
3. High temperature curing: Put the sprayed workpiece into the oven and bake it at 180-220°C for 15-30 minutes to melt, level and solidify the powder;
4. Post-processing: Check the coating after cooling to remove defects (such as sags and leaks).
--Main function

• Excellent protective properties: Aluminum coating has strong adhesion, high hardness, acid and alkali resistance, and salt spray corrosion resistance
• Environmentally friendly and pollution-free: no solvents, no formaldehyde, benzene and other harmful substances, meeting environmental protection requirements;
• Good decorative properties: The powder is rich in color and can achieve various effects such as matte, glossy, metallic texture, etc., and the coating is even.

--Core process
• Improve the performance of castings: For example, chromium plating is to improve the wear resistance and corrosion resistance of castings and enhance the appearance of castings. Nickel plating is to improve welding performance and corrosion resistance. Copper plating is used to improve electrical conductivity.
• Decoration and beautification: For example, gold plating and silver plating can improve the metallic luster and grade of the workpiece, and are suitable for precision parts;
• Dimension restoration: For workpieces that are worn or processed out of tolerance, the surface can be thickened through electroplating to restore the original dimensions and accuracy.
Zhonghuan can provide a full range of electroplating services.

--Core process
1. Pretreatment: degreasing → rust removal → phosphating → pure water washing (key, avoid electrolyte contamination) to ensure that the surface of the workpiece is clean and free of impurities, laying the foundation for coating adhesion;
2. Electrophoretic coating (electrophoretic deposition): Immerse the workpiece in the electrophoresis tank, connect the electrode (cathode electrophoresis workpiece is connected to the cathode), apply direct current (usually 0-400V), and the paint particles migrate directionally under the action of the electric field and are deposited on the surface of the workpiece to form a uniform coating;
3. Final rinse: ultrafiltration water washing (use the ultrafiltration system to recover excess paint and control conductivity), while recovering the bath liquid, flush the excess bath liquid that has not been deposited on the surface of the workpiece, saving consumables and reducing pollution;
4. Curing treatment: Pre-bake first (70-80°C) to remove moisture in the coating, and then perform high-temperature curing (170-180°C/30 minutes). In some scenarios, it can be heated in a curing furnace at 185-200°C for 15-20 minutes to melt, level and form a dense coating;
5. Post-processing: After the workpiece is cooled, decorative surface treatment can be selected according to needs to improve the appearance and texture of the product.
--Main function

• Super corrosion resistance: The coating is uniform and has no dead ends, and can cover the grooves and gaps of the workpiece. The salt spray test can last for hundreds of hours. It can effectively isolate air, moisture and corrosive media, and extend the service life of the workpiece;
• The coating has strong adhesion: it is closely combined with the metal substrate, not easy to fall off or peel, has excellent stability, and can resist external friction and impact;
• Environmentally friendly and efficient: The paint utilization rate is as high as over 95%, and an ultrafiltration system is used to recycle the tank liquid. There is no solvent evaporation, which complies with environmental protection requirements. It has a high degree of automation and is suitable for mass production needs.

--Core process
1. Pre-treatment: degreasing → rust removal → puttying (repairing surface defects) → polishing → masking (protecting non-spraying areas);
2. Spraying construction: first spray primer (to prevent rust and enhance adhesion) → spray mid-coat (fill in minor flaws) → spray topcoat (to determine color and gloss);
3. Curing treatment: Water-based paint can be dried naturally, while oil-based paint or industrial paint needs to be baked at low temperature (60-80℃);
4. Post-processing: polishing and waxing to improve surface smoothness.
--Main function

• Highly decorative: flexible color and gloss selection can achieve various complex appearance effects (such as imitation wood grain, matte);
• Wide range of application: not only suitable for metal, but also for plastic, wood and other materials, with simple construction;
• Protective function: It can isolate corrosive media and provide basic anti-rust and anti-scratch protection for the workpiece.

--Core process
1. Pretreatment: degreasing → rust removal → preheating (heat the workpiece to 300-400°C so that the plastic can melt and adhere);
2. Dip plastic treatment: quickly immerse the preheated workpiece into the molten plastic tank and stay for a certain period of time to allow the plastic to be evenly coated on the surface;
3. Solidification cooling: Take out the workpiece and cool it naturally or with air to solidify the plastic coating;
4. Post-processing: Remove excess plastic burrs and check coating thickness.
--Main function

• Ultimate anti-corrosion: The plastic coating completely isolates the metal from contact with the outside world, is acid and alkali resistant, and salt spray resistant, and is suitable for outdoor guardrails and steel wire mesh;
• Good insulation: the plastic coating is non-conductive and can be used as protective components for electrical equipment;
• Anti-slip and wear-resistant: The coating surface has a certain roughness and has anti-slip properties, and the plastic material is wear-resistant and anti-aging.

Detailed explanation of basic process types (GB/T 1173 / GB/T 25745) and core processes

--Core process
1. Annealing (T2)
Purpose: Eliminate casting stress, stabilize dimensions, improve cutting, and improve plasticity.
Craftsmanship:
Heating: 280–300℃ (aluminum silicon series)
Keep warm: 2–3h
Cooling: Cool to room temperature in furnace
Applicable to: complex castings, aluminum-silicon alloys that require machining (such as ZL102).
2. Solid solution treatment (quenching)
Purpose: Fully dissolve the strengthening phase (such as Mg₂Si, CuAl₂) into the aluminum matrix to form a supersaturated solid solution.
Key parameters:
Temperature: Aluminum-silicon series 520–560℃; Aluminum-copper series 530–540℃; Aluminum-magnesium series 460–490℃
Insulation: According to wall thickness, 3–5 min/mm, total time 2–12h
Cooling: 60–100℃ hot water (anti-deformation/cracking), transfer time <10s
Key points: If the temperature is too high, it is easy to over-burn (grain boundary melting); if the temperature is too low, the strengthening phase will not dissolve enough.
3. Aging treatment (precipitation hardening)
Natural aging (T4):
Leave at room temperature for 24–72h or longer
Strength gradually increases, good toughness, small deformation
Artificial aging (T5/T6/T7/T8):
Temperature: 150–200℃ (T6 commonly used 160–180℃)
Time: 3–8h (T6); T5 shorter, T7/T8 higher temperature/longer
Mechanism: supersaturated solid solution precipitates nanoscale strengthening phase, greatly improving strength
Risk: Too high temperature/too long time → over-aging (strength decreases, toughness increases).
--Process selection principles

1. Look at the alloy type
Can be heat treated and strengthened: Al-Si-Mg (A356/ZL101), Al-Cu-Mg (ZL205) → Priority T4/T5/T6
Not heat treatable: high silicon (ZL102), Al-Mn → only T1/T2/
2. Look at performance requirements
Maximum strength/hardness → T6
Strength + toughness + dimensional stability → T5
High Temperature/Creep Resistance → T7
Easy processing, low stress → T1/T2
3. Look at the casting structure
Thin wall/complex → shorten solution time, warm water quenching, choose T5 to prevent deformation
Thick/Simple → Can be fully strengthened by T6
Frequently Asked Questions and Control Points
Over-burning: The solid solution temperature exceeds the upper limit → melting of grain boundaries, coarse grains, and plummeting performance → Strict control of furnace temperature uniformity (±5°C)
Deformation/cracking: slow quenching transfer, uneven cooling → rapid transfer, use warm water, fixture support
Under-aging/over-aging: Strength is not up to standard or reduced → Make an aging curve based on the alloy to determine the optimal temperature/time
Oxidation/decarburization: Pass protective gas (N₂) into the furnace and control the heating rate
Standard basis
National standard: GB/T 25745-2010 "Heat Treatment of Cast Aluminum Alloy", GB/T 1173-2013 "Cast Aluminum Alloy"
National military standard: GJB 1695A-2019 (for aerospace use)