Application of Phosphating Primer in Metal Screen Printing

Metal screen printing, because the substrate is black or non-ferrous metals such as steel, iron, and copper. Aluminium, zinc, etc., have the common feature that the surface is apt to rust or oxidize, and the surface is relatively smooth, thus easily causing poor adhesion of the screen printing ink and the metal, as well as falling off. In order to solve this problem, a series of pretreatments (rust removal, cleaning, phosphating, passivation, etc.) must be performed, which not only consumes a lot of manpower and materials, but also prolongs the construction period. This book introduces a relatively simple method, that is, before printing silk, coating a layer of phosphatizing primer on the metal surface, not only can greatly simplify the pre-treatment process, but also can achieve the purpose of enhancing the ink adhesion. Phosphating primer, also known as washing primer, is a high-grade anti-rust coating made from polyvinyl butyrate resin and phosphoric acid, zinc chrome yellow, alcohols, etc. It is divided into single-component and two-component two (also known as single-liquid type and dual-liquid type), one-component phosphating primer can be self-formulated; two-component phosphating primer market is available for sale.
1. One-component phosphating primer.
1 recipe:
Material Name Percent (%) Weight (g)
Polyvinyl acetal glue 10.95 176.05
33. 3% aqueous solution of chromic acid 1.40 22.51
10% phosphoric acid acetone solution 10.95 176.05
Ethanol 62.20 1000.00
Butanol 14.50 233.12
(2) Preparation method: Add 33.3% lead-acid aqueous solution with proper amount of tri-alumina, add 2 times distilled water and mix evenly.
With an appropriate amount of phosphoric acid, a solution of 9 times acetone is a 10% solution of phosphoric acid in acetone, ready for use.
According to the formula ratio, ethanol and n-butanol are mixed, polyvinyl acetal glue is added, and the mixture is uniformly stirred to fully dissolve, and then added to the chromic acid aqueous solution and the phosphoric acid acetone solution, and can be used evenly after stirring.
2. Two-component phosphating primer.
1 Phosphating paint solution:
Material Name Weight (g)
Polyvinyl butyral 9
Basic zinc chromate (zinc chrome yellow) 8.625
Talc 1.375
Ethanol 60.875
Butanol 20.125
2 acidic phosphating solution:
Orthophosphoric acid (85% phosphoric acid solution) 4.5
Water (distilled water) 2.188
Anhydrous ethanol 18.312
3 thinner:
Ethanol (above 96% industrial alcohol) 90%
Butanol 30%

The two components of the two-component phosphating primer are stored separately. Phosphating lacquer liquid can be loaded into metal containers (iron drums), and phosphatizing liquids are put into non-metallic containers (plastic drums). When used according to the liquid paint, phosphating solution ratio of 4:1, that is, in 20% of the lacquer solution by adding 20% ​​of the phosphating solution (weight ratio), after stirring for half an hour, let it fully react and then use . And according to the amount of the construction amount, once used up, otherwise the remaining paint will fail after 12 hours, resulting in waste. If the phosphatizing primer used is too thick when used, the proportion of the two components cannot be changed. Some diluents may be added, and the diluent may also be used as a cleaning tool and a container.

3. Paint process requirements. Phosphating primers are used as corrosion protection for non-ferrous and ferrous metals. They can replace phosphating, but their coatings are thin. Generally, they are best controlled at 6 to 12 microns. The measured (circled method) adhesion can reach Class 1 standards, but its thickness can not exceed 100 microns, too thick but will affect the results. Phosphating primer has the characteristics of convenient construction and fast drying, and the coating also has good characteristics of flexibility, permeability, light resistance, and miscibility with some paints. Therefore, it can be used as a good bonding layer of metal and ink film in metal screen printing.