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Verfahren zur Herstellung einer Korrosionsschutzschicht auf Eisen und/oder eisenhaltigen Gegenstaenden

Production of anticorrosion coating on iron with good adhesion and weather resistance and reversibility - by precondensation of two silanes, one with uncurable and the other curable organo-functional groups, hydrolysis and condensation before dilution with organic solvent and application.
: Pilz, M.; Roemich, H.

Frontpage ()

DE 1996-19627223 A: 19960705
DE 1996-19627223 A: 19960705
EP 1997-109527 A: 19970612
DE 19627223 C1: 19970626
EP 816454 A: 19980107
Patent, Electronic Publication
Fraunhofer ISC ()

Production of an anticorrosion coating on iron and/or articles containing iron involves applying layer(s) containing a polycondensation product (I). (I) is prepared by (a) precondensation of 30-40 mole-% organic uncurable organo-functional silane of formula R'pSix4-p (II) with 60-70 mole-% organic curable organo-functional silane of formula R''m(R'''Y)n(4-m-n) (III) at 0-100 deg. C without externally added solvent; and (b) hydrolysis/condensation of this precondensate with a stoichiometric amount of water for 0.5-120 hours at 0-100 deg. C. In the formulae, R' = aryl; X = hydroxyl (OH), chlorine (Cl) or alkoxy; R'' = alk(en)yl, aryl, alk(en)ylaryl or arylalk(en)yl; R''' = alk(en)ylene, arylene, alk(en)ylarylene or arylalk(en)ylene; R'' and R''' may have oxygen (O), sulphur (S) or imino (-NH-) in the chain; X' = hydrogen (H), halogen, OH, alkoxy, acyloxy or -NR2; R = H or alkyl; Y = a polymerisable group; m, n = 0-3; (m+n), p = 1-3. Then (c) (I) is taken up in an organic solvent with a d ilution ratio (in wt.%) of (I) to solvent of 1:(0.1-10) and, if R'' = 3-glycidoxy propyl, 0.1-50 mole-%, with respect to (I), of an aminosilane is added as hardener; and (d) this solution is applied to the article in the form of layer(s), each 0.5-20 mu m thick. USE - The method is useful for conservation of metal articles in the open air ADVANTAGE - The coatings give better corrosion protection and reversibility than usual. A (II):(III) ratio of about 2:1 ensures that coatings used for conservation are reversible (i.e. can be removed with organic solvents). Polymerisation of the organic groups is inhibited and hence the degree of crosslinking is reduced. As a result, the surface polarity can be kept low, so that the coating is hydrophobic. The coating has good adhesion and is remarkably resistant to weathering, ensuring long-term protection.