The sealer has the following properties:
(1) The durability should be similar to that of the topcoat;
(2) Apply directly on the putty coating to fill small holes;
(3) While preventing pinholes, it can reduce the hygroscopicity of the secondary paste;
(4) Improve the fullness of the coating to a certain extent;
(5) It can prevent the matting caused by the unevenness and absorption of the surface;
(6) The primer itself is glossy, so it is easy to find the scratches on the paint surface optically;
(7) Better sandability than topcoat.
In order to achieve the above properties, the sealer often uses the same paint base as the topcoat, or uses polar resins, such as alkyd resins, amino alkyd resins, epoxy modified amino alkyd resins, and epoxy polyesters.
