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Powder Coating 101
A brief overview of the powder coating process
The process of finishing and protecting metal surfaces with dry powder coatings is not new. It has been used since the mid 1950's and began with the coating of pipe, for corrosion protection and electric motors for insulation. With the growing need to reduce air pollution (VOC’s), including that associated with thin film liquid coatings (spray paint), powder coating has become more popular.

 

Like any finishing or coating process, preparing the substrate for powder coating is absolutely critical.  The metal must be clean and free of all paint, dirt, and oils.  When restoring finishes, the first process is usually stripping by chemical or mechanical means.  If chemical stripping is used, the surface must be ‘roughed up’ using a blast media (‘sandblasting’) such as glass bead or Aluminum oxide.  After this step it’s essential to  prevent flash rust or corrosion from setting in.  For this step most powder coaters use a phosphate rinse or similar degrease/rinse agent.

 

The basic process used to apply powders to the substrate (the item being coated) is relatively simple in principle.  Anyone that has to deal with static electricity that attracts dust to TV’s and car finishes knows how positively charged particles stick.  In the powder coating process, very fine powder is fluidized and blown through a gun, and when it exits the tip the powder is positively charged with 15-100KV.  Meanwhile, the substrate is grounded through a cable, causing the charged powder to stick to it.  Anywhere powder is not desired must be plugged or masked with special high temp materials.

 

After application, the substrate is placed (generally hung) in an oven at temps between 350F and 400F where the powder ‘melts’ and flows.  Once the substrate reaches the specified temperature and dwell time (powder type specific), the powder ‘cross-links’, forming a tough finish.  The part is removed and is removed from the oven so it can cool.  Unlike paint, once the item is cool, it’s done and can be handled and/or used immediately.

 

Although powder coating has come a long way, it’s not yet a typical DIY (‘do-it-yourself’) process due to the cost of the equipment and the infrastructure required to get a professional result.  You can’t go down to Home Depot and buy a can of powder coating!  However, there are many ‘hobby guns’ out there and with a little ingenuity and a couple hundred dollars, you too can powder coat!

 

Powder coating is very durable and is available in hundreds of colors and finishes.  However, it is not indestructible as some people believe.  If the coating is chipped down to the metal, moisture and corrosion can get under the coating and cause problems.  If this happens, it’s important to seal the chip with a touch up paint.   Also, acetone or MEK will MELT powder coat finish as will other harsh chemicals, so care must be taken when cleaning powder coating finishes.

 

 

 

 

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