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Comparison of Methods for repairing color steel plates in clean rooms
2025/12/2
The following are professional repair methods for different types of damage, covering pre-repair preparations, specific operations, and post-repair verification to ensure that the repair meets GMP or relevant cleanliness standards.
The key prerequisite for the restoration of the clean area is "controlling secondary pollution". The following preparatory work must be completed first before starting the operation:
1. Environmental and tool preparation
Cleanliness level matching: According to the cleanliness level of the clean area (such as 10,000 grade, 100,000 grade), tools corresponding to the cleanliness level (such as stainless steel scrapers, lint-free cloths, special adhesives) should be used. All tools must undergo sterilization/dust removal treatment in advance (such as ultraviolet irradiation, alcohol wiping).
Isolation protection: Build a temporary isolation area with clean-grade plastic film (such as PE dust-proof film) to separate the repair area from other clean areas and prevent the spread of dust and debris. At the same time, activate the local FFU (Fan Filter Unit) to maintain positive pressure within the isolation area.
Personnel protection: Operators must wear protective clothing that meets the cleanliness level (such as sterile suits, dust-free gloves, and masks), and it is prohibited to bring non-essential items into the clean area.
2. Damage assessment: Clarify the repair plan
First, conduct a detailed inspection of the damaged parts of the color steel plate to determine the type and extent of the damage and avoid blind operation
Ii. Repair operations by type: From minor to severe damage
Minor damage: Surface scratches/pits (depth < 0.5mm, no structural damage)
It is applicable to situations where only the surface coating or substrate is slightly damaged and the color steel plate has not been penetrated. The core is "filling + color correction" to restore the surface integrity.
Cleaning and decontamination: Use a lint-free cloth dipped in 75% medical alcohol to repeatedly wipe the damaged area and the surrounding 10cm range to remove oil stains and dust, and avoid mixing in impurities when filling.
Filling and leveling: Select clean-grade epoxy putty (meeting FDA or GMP requirements, free of volatile harmful substances), apply it in small amounts multiple times to scratches/pits, and use a stainless steel scraper to smooth it out, ensuring it is flush with the surrounding surface. Let it cure (as per the putty instructions, usually 24 hours/room temperature).
Polishing and color correction: After curing, gently sand the surface with dust-free sandpaper of 400 mesh or above (grinding should be done in the isolation area to prevent dust from spreading) until it is smooth without any trace. If there is a color difference in the coating, a clean-grade color paint of the same material as the original color steel plate coating (such as polyvinylidene fluoride PVDF paint) should be selected. Apply it thinly 1-2 times with a dust-free brush, with a 12-hour interval between each coat for curing to ensure consistent color and no sagging.
2. Moderate damage: Joint cracking/seal failure (no substrate damage, only sealant aging)
The sealant for the joints of color steel plates in the clean area (such as wall panels and wall panels, wall panels and ceilings) is the core for preventing air leakage. If it ages or cracks, it should be replaced in time.
Old sealant removal: Carefully remove the aged sealant with a sterile blade (or a special sealant spatula) to avoid scratching the coating of the color steel plate. Then, wipe the seams with a lint-free cloth dipped in isopropyl alcohol to remove any residual glue residue and oil stains, ensuring the surface is dry (moisture content < 6%).
Select new sealant: Clean-grade silicone sealant must be used (food grade/pharmaceutical grade is preferred, such as Dow Corning 732, which is resistant to mold, has low volatility, and can withstand temperatures from -60 to 200℃). The use of ordinary industrial sealants (which are prone to releasing particles or VOCs) is strictly prohibited.
Sealant application: Load the sealant into a clean-grade glue gun and apply it evenly along the joint. The width of the sealant strip should cover both sides of the joint by more than 5mm, and the thickness should be controlled at 3-5mm. Use a dust-free scraper to press and scrape along the rubber strip to ensure that the rubber strip adheres closely to the surface of the color steel plate without any bubbles or gaps. Let it stand for curing (cure at room temperature for 24-48 hours. Do not touch during the curing period).
3. Severe damage: Local perforation/substrate damage (penetrating the color steel plate, affecting structure or sealing performance)
In such cases, local color steel plates need to be cut and replaced to ensure seamless connection with the original structure after repair.
Cutting positioning: At a distance of 5-10cm outside the damaged area, mark the cutting line with a marker pen (clean grade, erasable) to ensure that the new board replaced after cutting can completely cover the damaged area and that the edge aligns with the joint of the original board (to avoid creating new gaps).
Remove the old board: Use a dust-free electric saw (the saw blade needs to be disinfected in advance, and the local dust suction device should be turned on during cutting) to cut the old board along the marked line, and carefully remove the damaged part. If the keel (such as light steel keel) is involved, it is necessary to check whether the keel is deformed. If it is deformed, the keel of the same specification and clean grade (such as galvanized keel, with no burrs on the surface) should be replaced and fixed with stainless steel self-tapping screws (anti-rust, and the screw caps need to be sealed).
Installation of new plates: The new color steel plates should be consistent with the original plates in terms of material, thickness and coating (such as rock wool sandwich color steel plates, magnesium oxide sandwich color steel plates). Before installation, the surface of the new plates should be wiped with alcohol. Insert the new board into the cut notch and fix it on the keel with stainless steel self-tapping screws (with a spacing of 15-20cm). Apply a small amount of sealant to the screw caps (to prevent air leakage). At the joint between the new board and the original board, apply sealant according to the "joint crack repair" method to ensure there are no gaps.
Surface treatment: After the new board is installed, check if there are any scratches on the surface. If there are, fill, grind and recolor according to the "Minor Damage Repair" procedure to ensure a consistent overall appearance.
4. Special Damage: Coating peeling/rusting (substrate exposed, prone to particle formation)
It is commonly found in damp and clean areas (such as food processing workshops), and rust needs to be removed first before the coating is restored.
Rust removal treatment: If the rust is mild (only surface rust), gently sand and remove the rust with 320-grit dust-free sandpaper until a bright base plate is exposed. If the rust is deep (the substrate is dented), apply a clean-grade rust remover (such as phosphoric acid type rust remover, with no residue), let it stand for 10 minutes, then wipe it off with a lint-free cloth. After that, wipe it 2-3 times with clean water (purified water), and finally absorb the moisture with a dry lint-free cloth to ensure the substrate is dry.
Coating restoration: First apply clean-grade epoxy primer (1 coat, cure for 12 hours) to enhance the adhesion of the coating. Apply a topcoat of the same material as the original board (such as epoxy resin paint or PVDF paint) in thin coats twice, with a 12-hour interval between each coat for curing. Ensure that the coating thickness is consistent with the original board (usually 60-80μm), and there are no pinholes or bubbles.
Iii. Post-repair verification: Ensure compliance with cleanliness standards
After the repair is completed, three core verifications must be passed to avoid the situation where "the repair is qualified but the cleanliness does not meet the standards"Appearance and sealing inspection
Visual inspection: The surface of the repaired area should be smooth, free of scratches, and the color difference should be ≤ΔE2 (detected by a colorimeter). The sealant at the joint should be continuous without any breaks.
Air tightness test: Use a smoke generator to release smoke in the isolation area. After turning off the FFU, observe for 30 minutes. If there is no smoke leakage (especially at the seams), the sealing performance is qualified. Or use a pressure gauge to detect the pressure difference in the area to ensure that the pressure difference with adjacent areas meets the design requirements (for example, the pressure difference between the clean area and the non-clean area is ≥10Pa).
Cleanliness testing
According to the requirements of the clean area grade, use a particle counter to detect suspended particles in the repair area (for example, in the 10,000-level area, particles ≥0.5μm ≤3500 / L, particles ≥5μm ≤25 / L), and conduct three consecutive tests. If all tests meet the standards, it is qualified. If it is a pharmaceutical/food clean area, additional microbiological testing is required (such as sedimentation bacteria testing, with the colony count ≤1 per dish after 48 hours of culture).
Adhesion test
For newly applied coatings or putty, the adhesion is tested by the grid method (using a grid knife to make a 1mm×1mm grid and tearing with adhesive tape) to ensure that the coating does not fall off (adhesion grade ≥4B).
Iv. Precautions
To avoid secondary problems after repair, the use of non-clean grade materials is prohibited, such as ordinary putty, industrial glue, and non-food grade coatings. These materials are prone to releasing particles, VOCs, or breeding microorganisms, which can damage the clean environment.Control the repair time: Try to carry out repairs during the downtime in the clean area (such as equipment maintenance periods) to minimize the impact on production. If online repair is required, strict isolation must be carried out to avoid contaminating the product.
Record archiving: The repair process should be recorded in detail (such as the cause of damage, material model, operator, verification result) to form a "Clean Area Color Steel Plate Repair Record", which is convenient for subsequent traceability and GMP audit.
Through the above steps, it can be ensured that after the color steel plates in the clean area are repaired, not only will their appearance and structure be restored, but they can also meet the strict requirements of cleanliness and sealing, avoiding production risks (such as drug contamination and scrapping of electronic components) caused by improper repair.
