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Selection of surface coating for stainless steel strip and its impact on subsequent processing steps
source：www.cnlichao.net | Release time：2026年09月14日1、 Surface coating selection
1. Selection of substrate types
(1) PE polyethylene protective film (most commonly used)
Divided into low viscosity, medium viscosity, and high viscosity PE films. Suitable for 2B, BA, and brushed stainless steel strips; Advantages: Good flexibility, good followability, and less prone to brittle cracking during cutting and bending; Resistant to room temperature processing. Low viscosity: 8-30g/25mm; Medium viscosity: 30-80g/25mm; High viscosity: 80-150g/25mm.
Low viscosity PE: 8K mirror surface, high gloss BA surface to prevent residual glue;
Medium adhesive PE: ordinary 2B surface, brushed surface, slitting and bending processing;
High viscosity PE: deep drawing, intense stretching forming, no curling or bulging of the film during processing.
(2) PET polyester protective film
High temperature resistance, higher tensile strength, puncture resistance, suitable for high-temperature stamping and laser cutting processes; Price higher than PE. Mostly used for 8K mirror stainless steel strips and high-precision appearance parts. Disadvantages: Poor ductility, easy to crack and peel off when bent at large angles.
(3) CPP cast polypropylene film
Good transparency, solvent resistance, suitable for mirror stainless steel with strict control of residual adhesive, often used for precision decorative panels.
2. Core principles for viscosity selection
High gloss mirror surface, 8K polished surface: low viscosity film is selected, which is easy to tear after processing, reducing the risk of residual glue;
Brushed, 2B matte surface: viscosity can be selected;
Deep stretching, intense stamping, high-speed cutting: choose medium to high viscosity to avoid film warping and peeling during processing;
Excessive viscosity can lead to residual glue after high temperature or prolonged storage; Low viscosity leads to film slippage and edge formation during processing, resulting in loss of protective effect.
3. Other selection factors
Film thickness: conventional 30-80 μ m; Thin sheets and light processing should be selected with thin materials; Thick film is selected for thick strip, laser cutting, and polishing conditions;
Temperature resistance: ordinary PE can withstand ≤ 60 ℃; High temperature resistant PE/PET can withstand 100-180 ℃ in the short term and is suitable for laser cutting and thermoforming;
Storage period: Short term delivery (within 3 months) of regular PE; long-term inventory, high temperature environment in summer, using anti-aging and anti migration adhesive layer protective film to prevent adhesive layer penetration and residue;
Surface adaptation: Mirror stainless steel must use a low precipitation adhesive protective film to avoid adhesive migration and fogging on the surface.
2、 The impact of film coating on subsequent processing steps
1. Cutting process
The protective film can prevent cutting tools and pads from scratching the surface of the board during the cutting process; However, uneven film thickness and excessive adhesive force can increase the feeding resistance of the strip, which can easily lead to feeding slippage and uneven end faces; Stretching and wrinkling of the membrane edge can introduce foreign objects, slightly affecting the cutting accuracy; If the edge of the film is rolled over after slitting, it will contaminate the end face of the coil.
2. Bending, stamping, and deep drawing processes
The protective film deforms with the board, isolating the mold and preventing it from scratching the board surface. Negative impact: When the extensibility of the film is insufficient, the film cracks and partially peels off at the bent corner position, losing protection; After severe stretching, the adhesive layer of high mucosa is prone to remain on the surface of stainless steel; The superposition of film thickness will slightly change the gap between the sheet and the mold, and insufficient gap will increase the risk of indentation.
3. Laser cutting
The protective film can prevent cutting spatter slag from directly adhering to the stainless steel surface. PE film is not resistant to high temperatures, and the film burns rapidly at the cutting point, producing smoke and carbon deposits; Carbon deposits adhering to the surface of the board can cause local corrosion hazards if not cleaned thoroughly; PET high-temperature resistant film has less smoke, but higher cost; The residue of membrane combustion may adhere to the edge of the incision.
4. Welding process
The protective film in the welding area must be removed in advance; When welding with a film, the film decomposes under heat, producing a large amount of combustible smoke and carbon deposits, polluting the weld seam, easily producing pores and slag inclusions, and reducing the quality of the weld seam; The decomposition products will adhere to the surface of the board, making subsequent cleaning difficult.
5. Grinding and wire drawing processing
The protective film is not resistant to friction from grinding wheels and sand belts, and the film covering the polishing area will quickly break. Generally, it needs to be removed before polishing; If the film is partially retained, the damaged film fragments are easily embedded in the sand belt, affecting the uniformity of the processed texture.
6. Cleaning and degreasing process
Most protective films are not resistant to strong alkalis and organic solvents, and need to be peeled off before chemical cleaning; The solvent will penetrate the adhesive layer, causing residue and oil stains on the board surface.
7. Risk of film peeling and residual adhesive
High temperature, long-term storage, and exposure to sunlight cause the protective film layer to migrate, resulting in residual adhesive, watermarks, and foggy surfaces on the surface after peeling off the film; Residual adhesive can affect subsequent surface treatments such as spraying and passivation, resulting in poor coating adhesion.
3、 Key points for acceptance and usage control
1. Film covered appearance: no bubbles, wrinkles, leakage, or local peeling; The film and steel strip are evenly adhered.
2. Before processing, a small sample verification is required: simulate actual processing+peel off the film, check for residual glue and surface marks.
3. Control of finished product peeling time: Try to peel off the protective film as soon as possible after processing is completed. It is not recommended to store the protective film attached to the stainless steel surface for a long time.
4. The selection must be based on the stainless steel surface grade, processing technology, and storage environment specified in the technical agreement.
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