1.What are the principles and consequences of physical wear and scratches?
Principle: Accumulated dust particles (especially hard metal shavings, sand, quartz dust, etc.) will create "micro-cutting" and scratches on the coating surface under the action of wind, rain, foot traffic, or friction.
Consequences: These scratches will damage the smoothness and integrity of the coating surface. Minor scratches affect aesthetics, while severe scratches can penetrate directly through the topcoat and even the primer, exposing the metal substrate. Once the substrate is exposed, corrosion will begin.
2.What are the principles and consequences of "corrosion under dust"?
Moisture Retention: Dust is hygroscopic, creating a "humid microenvironment" on the coating surface. Even after the weather clears, the coating under the dust may remain moist for extended periods, creating conditions conducive to electrochemical corrosion.
Formation of Corrosion Cells: Some dust particles are chemically active (such as industrial dust containing chloride and sulfate ions, de-icing salt, etc.). When these dust particles dissolve in water, they form an electrolyte solution that can penetrate minute defects or scratches in the coating, triggering rapid pitting corrosion of the metal substrate.
Oxygen Concentration Cells: An oxygen concentration difference forms between the dust-covered area and the clean area, exacerbating localized corrosion.
Consequences: Corrosion occurs and spreads under the coating, generating metal oxides (rust), which are larger than the original metal. This expansion force "pushes up" the coating from within, causing blistering, cracking, and ultimately large-area peeling off.
3.What impact does this have on the adhesion and performance of the coating?
Hinders maintenance: If repairs or repainting are needed on the old coating, the adhering dust will severely affect the adhesion between the new and old coatings, causing the new coating system to fail prematurely.
Chemical corrosion: Some chemical dusts (such as strong acids and alkalis) can react directly with the resin in the coating, causing the coating to chalk, degrade, become brittle, and lose its protective ability.
4.Which type of dust poses the greatest risk?
High-hardness dust: Metal dust, sand, cement ash.
Highly hygroscopic or corrosive dust: Salt, fertilizers, chemical raw materials, industrial emissions (containing sulfur and nitrogen oxides).
Organic dust: Although less corrosive, it is prone to mold growth, and the resulting organic acids can damage coatings.
5.How to prevent it?
Regular cleaning: This is the most effective method. It is recommended to use low-pressure water rinsing and a neutral detergent (as discussed in previous questions) to gently remove accumulated dust from the surface. Avoid using high-pressure water guns to prevent water from entering crevices.
Design optimization: Consider dust-proofing features in building designs, avoiding recesses and horizontal surfaces that easily accumulate dust.
Choose a suitable coating: In dusty industrial areas or coastal regions, choose coatings with better self-cleaning properties and a smoother, harder surface (such as PVDF fluorocarbon coatings) to reduce dust adhesion and facilitate rainwater washing away.
Promptly address scratches: If scratches or damage are found on the coating, repair them promptly with a specialized repair paint to seal the damaged area.