Abstract: Chemically resistant coatings comprise a binder, the major portion of which is prepared by reacting, in the presence of an acidic solution, trialkoxysilanes with aliphatic polyols and/or silicone intermediates. The silanes have the formula ##STR1## where R.sub.1 is selected from the group consisting of alkyl, aryl and cycloalkyl groups containing up to about 6 carbon atoms and each R.sub.2 is independently selected from the group consisting of alkyl, hydroxyalkyl, alkoxyalkyl and hydroxyalkoxyalkyl groups containing up to about 6 carbon atoms. The aliphatic polyols contain an average of at least two carbon bonded hydroxyl groups per polyol. The silicone intermediates have the formula ##STR2## WHERE EACH R.sub.3 is selected from the group consisting of the hydroxy group and alkyl, aryl, and alkoxy groups having up to about 6 carbon atoms. Each R.sub.4 is selected from the group consisting of hydrogen and alkyl and aryl groups having up to about 6 carbon atoms.

Abstract: Compositions for protecting materials from growth of pestiferous organisms, and particularly for protecting marine surfaces from fouling organisms, are formed from precursors having the formula ##STR1## where m is from 1 to about 10, where each X is independently selected from the group consisting of alkyl and alkoxyalkyl radicals containing less than about 6 carbon atoms and Y, where Y has the formula ##STR2## where R.sub.1, R.sub.2 and R.sub.3 are independently selected from the group consisting of alkyl, cycloalkyl, and aryl radicals, where R.sub.1, R.sub.2 and R.sub.3 contain in combination up to about 18 carbon atoms. The ratio of the tin atoms to silicon atoms in the precursors is at least about 1:50.The precursors can be directly used as an additive for coatings. The precursors can also be used by subjecting them to hydrolysis and polycondensation to form an organotin substituted polysiloxane for use as an additive and a binder for coatings.