What Are the Common Problems and Precautions in the Construction of Steel‑Structure Fire‑Retardant Coatings?

I. Major Problems Existing in the Construction Quality of Steel‑Structure Fire‑Retardant Coatings
Fire‑retardant coatings are applied onto steel components by professional engineers to form fire‑resistant layers, completing the whole fire‑proof coating process for steel structures. The construction of fire‑retardant coatings can be regarded as the secondary production of such coatings. Improper construction will compromise the quality of steel‑structure fire‑retardant coating projects. The key on‑site construction problems are listed below:
Neglecting surface cleaning of substrates impairs the performance of fire‑retardant coatings.
Construction teams lack valid construction qualifications despite sufficient technical capacity.
No scientific construction plan is formulated prior to work, and construction quality is not inspected in strict accordance with technical standards during implementation.
Final acceptance of fire‑retardant coating projects merely relies on visual inspection and coating‑thickness measurement, without rigorous acceptance criteria and testing methods.
Excessive pursuit of surface appearance and smoothness, such as polishing fire‑retardant coating surfaces or applying ordinary decorative paints over them. These practices make it hard to guarantee the technical performance of fire‑resistant coatings.
II. Precautions for Construction of Steel‑Structure Fire‑Retardant Coatings
Substrate surface cleaning for fire‑retardant coatings shall be treated as a mandatory working procedure with strict inspection. Remove dust, iron filings, rust, grease and other substances that hinder adhesion, and complete anti‑rust treatment for substrates. The primer and topcoat of fire‑retardant coatings shall be well‑matched, and the primer shall not cause corrosion to steel materials.
For spraying fire‑retardant coatings, control coating consistency, air‑compressor pressure, and the distance between spray nozzles and steel components. Excessive splashing during spraying indicates unreasonable construction parameters, which shall be adjusted in time. Do not add excessive thinner, otherwise the normal construction viscosity will decrease and the coating will fail to adhere to steel‑structure surfaces.
Fire‑retardant spraying protection for steel structures shall be performed by well‑trained and qualified construction teams. Rigorous construction plans shall be formulated according to project characteristics and selected products. Physical and chemical properties of coatings can be tested with sampled materials in specified proportions before construction. For intumescent fire‑retardant coatings, foaming performance shall be tested at different positions during construction.
Upon project completion, besides coating‑thickness measurement, visual inspection shall be carried out for coating color, leakage and cracks. A 0.75‑1 kg hammer shall be used for tapping tests to check coating strength, and a 1‑meter straightedge shall measure surface flatness. Qualified coatings shall feature smooth surfaces without obvious depressions, firm bonding, no pulverization, looseness or floating mortar. Protrusions shall be removed, and no missing coating, powder falling or prominent cracks are allowed.
For multi‑coat application, apply subsequent coats only after the previous coat is basically dried and cured. Coating protection measures, number of coating passes and protective‑layer thickness shall comply with construction‑design requirements. Each coat shall be applied with moderate thickness; excessive thickness or uneven rolling shall be avoided to prevent poor coating quality. Construction shall follow coating procedures strictly. Do not rush construction progress at the cost of potential safety hazards for buildings.
Coating thickness shall meet design values, and joints shall be thickened. Spraying‑site requirements, component‑surface treatment, joint filling, coating preparation, number of spraying passes, quality control and acceptance shall all comply with the current national standard Technical Specification for Application of Fire‑Retardant Coatings for Steel Structures (CECS24‑2020). Coating thickness shall be inspected with thickness gauges during construction. In case of widespread wide cracks on coatings, analyze whether construction procedures and coating mixing ratios are appropriate.