a coating and devices using the coating are provided . the coating is applied in liquid form and dried or otherwise cured to form a durable adherent coating resistant to high temperatures and having optional hydrophobic properties . the coating formulation contains an aqueous formulation of silica , one or more fillers , and sufficient base , , to have a ph exceeding about 10 . 5 during at least part of the formulation process . the formulation may contain a compound that affects surface free energy , energy to make the cured coating hydrophobic . such compounds include silanes containing halogens and in particular silanes containing one or more hydrolyzable groups attached to at least one silicon atom and a group containing one or more halogens . a medical instrument may be at least partially covered by a coating using the formulation .