wavey finish on powder coat???

[redsun]

I have been powder coating for a few months now. A freind of mine brought over a peice that a freind of his had coated at another shop that has been coating for years. I noticed his part was smooth like glass. Mine always comes out a little wavey like say a new peice of leather. they look good but what do i need to do to get it smooth like glass? We both use tiger powder and this part was coated with bengal gloss black which i have used several times with waveyish results. I use a 100kv gema gun and cure to instruction at metal temp. i have a 4x4x6 electric oven. I do keep the gun turned all the way up, mabe the problem? Thanks for yalls help!! Love the site by the way!!

[SCOTTRODS]

I have been powder coating for a few months now. A freind of mine brought over a peice that a freind of his had coated at another shop that has been coating for years. I noticed his part was smooth like glass. Mine always comes out a little wavey like say a new peice of leather. they look good but what do i need to do to get it smooth like glass? We both use tiger powder and this part was coated with bengal gloss black which i have used several times with waveyish results. I use a 100kv gema gun and cure to instruction at metal temp. i have a 4x4x6 electric oven. I do keep the gun turned all the way up, mabe the problem? Thanks for yalls help!! Love the site by the way!!

Could be a variety of things causing your "orange Peel" appearance. Likely too much or too little powder, or too fast or too slow ramp up or "soak time" at flow out temp..... Experiementing can find the way. I like to heat my oven to 250 and put the part in til it reaches 250 and then turn up to cure temp slowly after it has time to "soak a little"

[UtahPowderCoatings]

I agree with SCOTTRODS on the too much powder possibility (based on the available info). We also use Tiger powders, including their "Bengal" series. I used Bengal Orange on a recent project and I did not see the orange peel or wavy texture. I have had VERY good luck while using Tiger's Wet Black for a chopper frame. It came out like glass!

Do you have a Dry film thickness gauge? Like this one from Delfesko? DeFelsko Home Page



It will really help to determine your mil thickness before your part goes in the oven.

Good Luck!

[redsun]

no, i dont have a gauge but feel pretty strong that Im not useing too much powder. What do you think about his other comment of heating it to 250 then upping the fire to cure. sounds logical.

[bake]

I wondered how the gauge worked, so would that piece in the gif be 225 mils (or less) thick then? How do you use it on round or curved surfaces?

[redsun]

Ya it would be 225 microns. It has to be used on a flat surface but like a tube you could run parallel with it. cant be used on round or curved surfaces and it only tells you how thick it is in the spot that you check and you have to reshoot that spot anyway cause you just screwed it up with the gauge. Thats why I dont use them..

[baz]

i use both a gema and a wagner and with both systems i get smoother results when i lower the voltage to about 30kv

[UtahPowderCoatings]

no, i dont have a gauge but feel pretty strong that Im not useing too much powder. What do you think about his other comment of heating it to 250 then upping the fire to cure. sounds logical.

I have to admit, I don't see the logic. I believe he may be referring to "thermoplastic" powder. The particles in that type of coating are more or less melting together in the oven to form their bond. Similar to pouring some sugar into a pot and waiting for the granules to eventually melt together. It's the way powders used to be made and they are far less common than the "thermoset" powders most companies sell today. Thermoset powders need to reach cure temps in order to start a chemical reaction within the powder particles, releasing the bonding agents and achieving a full "set" or cure. An everyday example might be two part epoxy you have to mix together so a reaction can occur, causing the glue to harden. That's why letting them simmer at a lower temperature does not make sense to me.

One way to test this is to re-heat your part. Thermoplastic powders will remelt each time you bring it up to temperature whereas thermoset powder will resist remelting if the coating has fully cured. Tiger Drylacs Bengal series is a TGIC polyester, which is a thermoset powder.

Is there any texture, or high and low spots, to the powder while it's still dry? Like "cratering" where it starts to look like the surface of the moon? That's from to high Kv setting OR being too close to the part OR going over it too many times. Like baz explained above, using 30 Kv can allow you to be closer to the part or make more passes without having back ionization (cratering).

it only tells you how thick it is in the spot that you check and you have to reshoot that spot anyway cause you just screwed it up with the gauge. Thats why I dont use them..

Or you could spray a scrap piece at the same time using the same technique and test thickness on that piece

[redsun]

Im gonna play with it today and ill post some pics.

[SCOTTRODS]

Pretty much all powders have a "flow characteristic" that is specific to that powder.... as well they have other cure characteristics. Cure is a series of those chemical "actions" and "reactions".

Some Powders have a narrow range of temps to flow out. This is not just a "melt" item,.... It depends on the flow agents and other chemistry in the powder used, how long it will flow out in the typical cure cycle recommended by the manufacturer.

In other words,.... All powders do not act the same at the temperature ramp-ups. Some will flow quickly and level out nicely with a "stick it in the oven and go" cure.... others can use a slower ramp up, to allow for a longer flow out temp..... Finding that flow out temp is difficult to say the least, so starting at what I do (the 250 degrees) is a low guess.... to say the least.... slowly ramping up from that point, is my way of "finding" the flow out temp and allowing a longer flow time on some powders.

I'm still searching for the basic curing stages. I know I have them somewhere, but I'm having a difficult time finding them and will likely have to search the net for them as I recently had a Computer crash and had to re-load windoze..... where I moved the files to is a mystery, as I was in a state of mind that didn't give much thought to the future other than just "save the stuff somewhere". Once I find it, I'll share.... It will make sense too, if the above doesn't do a good job already (I think it needs some help to be better explained).