Uses for Lithium Silicates and Polysilicates

Some of the difficulties involved in using zinc-rich paints bonded with polysilicates were reviewed by Wright (117). who pointed out that in storage, slow reaction of zinc with the vehicle on aging reduced the quality of the final coating. 

Several types of soluble silicates were evaluated, but a lithium polysilicate with 

Si0j Li20 ratio about 5 1 was satisfactory, using zinc dust of 2-3 micron particle size. The advantage of lithium was mainly that the mixtures are more stable (118). 

The binder properties are useful in other pigmented coatings such as clay-based paints (119). The zinc-lithium silicate coatings can be applied by anodic electrodeposition on steel (120). In another-typc of use, lithium polysilicate provides an intermediate bond between the fluorocarbon polymer coating and metal on antisticking cook ware (121). 

The precipitation of higher-ratio insoluble silicates from hot solution may be used to deposit siliceous coatings on hydrophilic surfaces. Sams (122) discloses that silica-rich coatings for optical or protective effects are deposited on surfaces such as glass from 2 1 ratio lithium silicate solution when the surface is immersed in the solution as it is heated to 95 C. Even after 10 sec, there is formed a colored film showing light interference, which must be of the order of 0.3 microns in thickness. Solutions with ratios from 1.3 1 to 10.7 1 may be used. 

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