Why Do Metal and Plastic Coatings Peel Off? How to Solve It?

Why Do Metal and Plastic Coatings Peel Off? How to Solve It?

Coating peeling and flaking are common defects for sprayed metal and plastic workpieces, which damage appearance and weaken anti-corrosion performance. Most peeling problems stem from non-standard processing instead of defective coatings, including pretreatment, spraying and curing errors. Targeted solutions can effectively avoid repeated quality failures.

Inadequate pretreatment is the top cause. Residual oil, rust and phosphating residue on metal surfaces, as well as release agents on plastic parts will separate coatings from substrates. Besides, plastics feature low surface energy. Without corona or flame activation, coatings fail to bond firmly. Excessively polished metal surfaces also reduce coating adhesion.

Improper spraying and curing also lead to peeling. Excessive dust and high humidity in spraying workshops cause uneven coating adhesion. Unqualified curing temperature and time will make coatings brittle or incompletely cross-linked. In addition, mismatched coatings for metal and plastic substrates will trigger compatibility peeling.

To fix the problem, conduct thorough degreasing and dust removal before spraying. Activate plastic surfaces and adjust workshop humidity reasonably. Follow official curing parameters for different substrates. For peeled workpieces, polish off residual coatings and redo the whole pretreatment and spraying process instead of simple touch-up.