Painting and renovation of steel structure factories is a systematic project involving multiple links such as rust removal, corrosion protection, and coating.
1. Preliminary evaluation and preparation
Structural inspection
Check whether the steel structure has deformation, cracks, and rust degree (mild rust: surface floating rust; moderate: rust pit; severe: rust perforation).
Record the problems of welds and bolts that need to be repaired, and give priority to structural reinforcement.
Environmental Assessment
Confirm the purpose of the factory (such as the chemical and food industries that have special requirements for coatings).
Analyze corrosion factors: moisture, acid and alkali gas, high temperature, etc., and select the corresponding coating.
Paint selection
Primer: epoxy zinc-rich primer (strong corrosion resistance), reddish anti-rust paint (low cost but lead, use with caution).
Intermediate paint: Epoxy cloud iron intermediate paint (reinforced thickness and adhesion).
Topcoat: Polyurethane topcoat (good weather resistance), fluorocarbon paint (extra long weather resistance, suitable for harsh environments).
Special requirements: Fire-retardant coatings (needed to be constructed separately, such as expansion fire-retardant coatings).
2. Construction steps
Surface treatment (key steps)
Hand tools rust removal (St2 level): Wire brushes and shovels to treat loose rust layers, suitable for small areas.
Mechanical rust removal (St3 level): Angle grinder, sandblasting (Sa2.5 level is more thorough), sandblasting is recommended to treat
complex components.
Clean the surface: Use solvents (such as acetone) to remove oil and dust.
Fix defects
Fill weld pores and pits: Use epoxy putty or metal filler.
Replace severely rusted steel plates (corrosion exceeds 30% of the original thickness and need to be replaced).
Primer coating
Mix epoxy zinc-rich primer (strictly formulated in proportion) and mature for 10-15 minutes.
Spray or brush, dry film thickness ≥60μm to ensure full coverage.
Recoating interval time (refer to product instructions, usually 4-8 hours).
Intermediate paint and topcoat construction
Apply 1-2 intermediate paint to increase the thickness of the coating system (the total dry film thickness is recommended to be 120-200μm).
Check whether the primer is completely cured before the topcoat is constructed to avoid biting the bottom.
It is recommended to spray the topcoat to ensure uniform color and avoid sagging.
3. Things to note
Construction conditions
The ambient temperature is 5-35℃, and the humidity is ≤85%, so as to avoid rainy, snowy and strong winds.
The surface temperature of the steel must be above 3℃ above the dew point to prevent condensation.
Safety measures
High-altitude operations require scaffolding or high-altitude operation vehicles and seat belts.
Wear protective clothing and goggles during sandblasting to avoid the risk of silicosis.
Open fires are strictly prohibited in fire-proof areas, and paints are stored away from the fire source.
Quality control
Use a thickness gauge to detect the coating thickness and spot check the coverage.
Acceptance standard: ISO 12944 or GB/T 8923 (no leakage, bubbles, pinholes).
4. Frequently Asked Questions
Rust-returning problem: Incomplete removal of rust can be caused by re-sanding until the metallic luster is required.
Coating sheds: Inadequate surface cleaning or the primer is not cured, and local rework is required.
Sleeping: Spraying distance is too close or diluent is too much, repair after sanding.
5. Maintenance suggestions
Check the coating status every year and locally repair the paint (such as the edges and welds are prone to rust first).
Regularly clean the dust in the house,
