The curse of black chrome.

[Guest]

I'm having some major issues with black chrome.

When we do a part in black chrome, we get these little black dots maybe 1/8" in diameter. Some times the parts will also have weird powder patterns, or other small issues.

So far we have tried:
Brand new coalescing filter with/20 cfm rated dessication dryer
Inline filters
Different powder (both new powder from PBTP & others)
Different hopper, new hoses (in case it was contamination)
Different gun settings (from 2 bars to max on the HS)
Letting the metal cool down to almost ambient temp

Pretty much I'm about to stop offering this color to customers because we have such trouble with it.

[JHForman]

Re: The curse of black chrome.

I get these little black dots also. Which black chrome are you using currently? does any other color you shoot do anything strange?

[Guest]

Re: The curse of black chrome.

a pic would be helpful

[Guest]

Re: The curse of black chrome.

what powder coating gun are you using?

[Auto-Cycle PC]

Re: The curse of black chrome.

Pics would help but it sounds like some contamination. I have seen these before with black chrome and they usually dont show up until about 3/4 cure.

[JHForman]

Re: The curse of black chrome.

what powder coating gun are you using?

Different gun settings (from 2 bars to max on the HS)

[Guest]

Re: The curse of black chrome.

Gun is a columbia hyper smooth 02.

KV settings have been varied from 2 bars on the HS, to almost max with no difference.

No other powder give me any trouble.

The powder I've been using is the Black Chrome 1 from PTBP. I've also tried the columbia coatings black chrome with the same result, and brand new powder from columbia with the same problems. (was shot from a new hopper, with new hose as well just to make sure it wasn't contamination).

We've also tried laying down the KL Killer primer to make sure it's not contaminates in the metal causing this.

I also tried shooting it with my friends caswell gun with pretty much the same result.

I'll post some pics up as soon as they upload

[JHForman]

Re: The curse of black chrome.

possible bad ground? I am only guessing here. also what about shooting the part ungrounded?

[JHForman]

Re: The curse of black chrome.

You also said "wierd powder patterns". What's the gun to part distance when you shoot? Are these spots random over the part or are they in buches in certain areas?

I'm gonna wait for the pics.

oooo the suspense is killing me

[Guest]

Re: The curse of black chrome.

Gun has the ground running to a 4' copper pipe in the ground outside the shop.

Seems to do the same thing with the part grounded/un grounded.

Parts are shot from as far away as possible to reduce blowing the powder off ect.







Sorry about the wait, it takes for ever to upload pics as the shop only has dial up (no cable or dsl in our location, it's either dial up or my own t1 for 500$ a month)

[JNZFinishing]

Re: The curse of black chrome.

I've had the same probs with BC in the past and have found that its usually excess outgassing, especially on VC's. Doing a 2nd coat usually fixes it.

[Guest]

Re: The curse of black chrome.

Valve covers, wheels, bottles it does it all the same.

Prep is the same as any other part I do or better.

Stripped with the industrial stripper from columbia, sand blasted with 70 grit alum oxide, de greased with auto body quality prep solvent or lacquer thinner. Then out gassed for 30 minutes Part metal temp at 400.

That particular valve cover was sprayed over 2 coats of out gas killing primer that were both cured for 30 minutes, and the part was out gassed before I started on it.

[JHForman]

Re: The curse of black chrome.

Valve covers, wheels, bottles it does it all the same.

Prep is the same as any other part I do or better.

Stripped with the industrial stripper from columbia, sand blasted with 70 grit alum oxide, de greased with auto body quality prep solvent or lacquer thinner. Then out gassed for 30 minutes Part metal temp at 400.

That particular valve cover was sprayed over 2 coats of out gas killing primer that were both cured for 30 minutes, and the part was out gassed before I started on it.

your outgassing temperature needs to be a little higher, as for the black spots, i have never found an answer/solution to this. it was hit or miss. Have you tried using PBTP bonded black chrome? just curious.

[Guest]

Re: The curse of black chrome.

That is the PTBP bonded black chrome.

What temp to do you guys recommend for out gassing? I feel bad pushing the aluminum to 400 as it is, as I've heard that the aluminum can have problems when heated.

The parts do not usually get degreased before stripping.

[wiseguyz]

Re: The curse of black chrome.

I agree with Harleydad. The wierd powder patterns also look to me like oil contamination. On aluminum valve covers, I normally degrease, strip, outgass, blast, then wash thoroughly with warm soapy water, rinse very well and blow dry with compressed air, oven dry and coat.