PROTECTIVE COATINGS ON ALUMINUM BY SPONTANEOUS POLYMERIZATION

A novel process to form protective polymer coatings on aluminum using spontaneous polymerization is described. When an aluminum sample is im mersed in a partly aqueous monomer solution, polymerization proceeds r apidly on the metal surface, without the addition of initiator, at roo m temperature. The polymer coatings studied here were formed using sty rene (St), N-phenyl maleimide (NPMI), 2-methacryloyloxy acetoacetate ( MEA), and bis-maleimide (BMI), monomers, from solutions of different c ompositions. A possible mechanism for spontaneous initiation and propa gation is proposed. The effects of process variables such as polymeriz ation time, monomer concentration, and monomer ratios in feed on the c oating thickness and properties are presented. The glass transition te mperatures, adhesion strength to aluminum, thermal stability and corro sion resistance of these coatings are reported. The coatings obtained are up to 50 mu m thick and conform to the shape of the substrate. The y have excellent thermal stability, low dielectric constant, and show very good resistance to corrosion under the ASTM B-117 accelerated sal t fog test. Other monomers and metals may also be used.