What precautions should be taken when using metal powder coatings
1。 Coating Method of Metal Powder Coatings
In most cases, electrostatic spraying gun is used for painting. Because this type of product contains metal pigments, the outstanding grounding of the system should be ensured during the construction of electrostatic gun, and a lower electrostatic voltage and powder output should be set together to avoid sparking during spraying. The function of the coating is closely related to the setting, quality or brand of the spray gun. After a long time spraying, a lot of metal powder may accumulate at the discharge needle of the spray gun, requiring the builder to tidy up the discharge needle on time.
2. Gloss of Metal Powder Coatings
In most cases, because of the great errors, it is not advocated to use glossometer to measure the gloss of metal surface coating, but only to use visual contrast method to judge whether it is the same as the standard sample。
3. Recyclability of Metal Powder Coatings
As for the powder made by dry mixing method, there will be different phenomena in the spraying and recycling process, so there will be certain differences in the content of metal pigments between the recycled powder and the new powder, which may lead to different appearance of the coating film and show a color bias phenomenon。 This is due to the different properties between metal pigments and powder particles。 Experts advocate that the ratio of recycled powder to new powder should be at least 1:4。 If the powder coatings made by bonding and fixing method have a relatively fixed ratio between metal pigments and powder particles, the powder can be recovered from scratch。
4. Shielding of Metal Powder Coatings
Re-spraying coatings on metal powder coatings has the following benefits: enhancing the stone-strike resistance of metal powder coatings; adding the beautiful effect of metal powder coatings; thoroughly treating the erasability of metal pigments; and advancing the weatherability of metal powder coatings. In order to ensure the appearance of the covering layer, it is required that the workpiece sprayed for the first time should not be polluted. As a result, there is a general need for fully automated spraying lines and two separate spraying rooms to be painted separately. It is advocated that the coating should not be sprayed normally. Only when the requirements are very high, such as: high-grade household appliances, car wheels and field use (to ensure weather resistance), etc.
5. Scrapability of Metal Pigments
Whether the powder is made by dry mixing method or by bonding and fixing method, the erasability of metal pigments can not be thoroughly dealt with。 The only way to treat the erasability is to spray a transparent coating on the metal powder coating。
6. Ways to Keep the Appearance of Metal Powder Coatings Together
6.1 For the same product, try to use the same batch of metal powder coatings to avoid the problem of batch difference between powder coatings.
6。2 Maintain the stability of spraying conditions as far as possible。 Using the same set of spraying equipment, using the same voltage, pressure and other parameters; keeping the spacing between spraying gun and workpiece as constant as possible, keeping the stability of film thickness as far as possible; ensuring that the powder coating before spraying has been fully fluidized; using recycled powder, should ensure that the ratio of recycled powder to new powder is at least 1:4; avoiding the use of metal powder coating spraying chaotic or deep depression of the work。 It is advocated that spraying should be carried out together for multiple parts to be assembled together。
The article is from Metal Powder Coatings: http://www.kksao11.com/