High edge cathodic epoxy electrocoat composition
An electrocoating composition and a coating formed from the composition are described herein. The electrocoating composition includes at least an epoxy resin component, an isocyanate-functional component and a silica-based additive. The coating shows about 40 to 70% reduction in edge corrosion relative to a conventional coating.
1. A coated article, comprising:
a cold-rolled steel substrate with sharp areas produced by laser cutting;
a coating disposed on the substrate, wherein the coating comprises
an electrocoat composition comprising an epoxy-functional compound;
an isocyanate-functional compound;
a dibutyl tin oxide catalyst; and
a wax after-treated precipitated silica, wherein the coated article shows about 40 to 70% reduction in edge corrosion according to SAE J2334 cyclic corrosion test procedure relative to a coated article with a coating applied thereon that does not include the after-treated precipitated silica.
2. The coated article of claim 1 , wherein the epoxy-functional compound is an amino-based cationic salt moiety formed from an amine compound selected from primary amines, secondary amines, tertiary amines, and combinations thereof.
3. The article of claim 1 , wherein the isocyanate-functional compound is a blocked isocyanate.
4. The coated article of claim 1 , further comprising one or more components selected from pigments, film-forming agents, surfactants, wetting agents, defoaming agents, rheology-modifying agents, colorants, or combinations thereof.
5. The coated article of claim 1 , wherein the after-treated precipitated silica is present in an amount of about 1 to 30 wt %, based on the total weight of solids in the coating composition.
6. The coated article of claim 1 , wherein the coating composition comprises: a resin part comprising the epoxy-functional compound and the isocyanate-functional compound; and a paste part comprising at least the silica-based additive.
7. The coated article of claim 6 , wherein the coating composition comprises a ratio of the paste part to the resin part from about 1:2 to about 1:5.
8. A method of making the coated article of claim 1 , the method comprising: depositing the coating composition onto the substrate with a cathodic electrocoating process; and at least partially crosslinking the epoxy-functional compound and the isocyanate-functional compound.