Aluminum is a common basic material in the field of building materials and is widely used in our lives. Therefore, it is necessary to spray powder on aluminum to protect it from corrosion.Next, I will describe in detail the steps and methods of coating aluminum.
Surface Pretreatment
Aluminum surface oil, dust and even oxidized layer, just like a dirty bowl is not washed directly serve food will not be able to stain the food, not clean will lead to the powder can not be firmly adhered to the
Use alkaline degreasing agent to remove oil and grease on the aluminum surface, together with two counter-current water washing to remove the residue thoroughly.
Through the ionic phosphate or zirconium-based treatment to form a 0.5-1μm chemical conversion film to improve coating adhesion by more than 30%, chrome-free passivation is more environmentally friendly and enhances corrosion resistance, microporous structure facilitates the penetration of powder.
On the basis of the completion of the first two steps, you can go to the option of sandblasting the aluminum surface.
Spray Powder
Why use static electricity?
The powder itself is not electrically charged, but the spray gun charges the powder like a “magic wand”. The charged powder acts like iron filings attracted by a magnet and adsorbs evenly on the surface of the aluminum.
What to look for?
Distance: the spray gun from the aluminum about 15-30 cm, too close to the “fire”, too far away from the spray is not uniform.
Difficult to spray corners: Complex shapes of aluminum (such as grooves) need to rotate the spray or adjust the angle to avoid “dead ends”.
Curing process
Why the heat?
The powder is sprayed on loosely and needs to be baked at high temperature (about 180-210°C) for 20 minutes to allow the powder to melt and solidify into a firm coating, just like a cookie that becomes crispy after baking
Also remember this parameter polyester powder 180-210 ° C, epoxy powder 160-190 ° C, curing time of 15-25 minutes, because the temperature is not enough to lead to incomplete cross-linking of the resin, the mechanical properties of the decline; too high is triggered by yellowing or thermal aging
Quality testing
Check what?
Thickness: Use an instrument to measure whether the coating is uniform (generally 40-120 microns, thinner than a hair).
Firmness: use a razor blade to scratch the grid to see if the coating will fall off in pieces (like checking whether the cell phone film is edged).
Appearance: Naked eye to see whether there are bubbles, color difference, whether the luster is consistent.
Packaging, storage and transportation
Laminating Packaging:
Use PE protective film with tensile rate ≥300% to avoid transportation scratching. Reason: Aluminum profile surface is easy to scratch, affecting the aesthetics of the end product.
Storage conditions：
Temperature 10-35℃, humidity ≤60%, prohibit stacking more than 5 layers. Reason: High temperature and high humidity environment is easy to cause hydrolysis or blistering of the coating.
