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Tricks to minimize outgas?

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  • drfjr1976
    replied
    OOPS! I didn't even look at the dates of the posts. I was wondering why Tom was having this kind of trouble. I was actually kind of shocked.

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  • non-stick
    replied
    by the way.... Scot (rivermaster)... I havn't seen you post in a long time but by co-incidence see you here today. Funny how things happen like this. Good work on the chipper in the album,bud. Just wanted to say it was nice "seeing" you again.... Russ

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  • non-stick
    replied
    wow.... this post is a blast from the past,huh? A basic guide ( and the "why" this happens) to this same process can be found in the tips and tricks section as well. Pretty neat to see the old posts revisited once in a while,huh? Shows you how far one has come in a short amount of time with a little help from these boards.

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  • drfjr1976
    replied
    Here are the steps I use when I do aluminum castings.
    #1 Degrease
    #2 Media blast with silica sand
    #3 Clean with acetone
    #4 Dry/outgas in oven at 400 for 20-25 minutes
    #5 Let part cool completely than reclean with acetone to remove any thing that may have came to the surface during drying/outgassing
    #6 Place in oven once again, this time at 375 for 10 minutes
    #7 Remove part and coat before the temp drops below 150 so that it will pull the coating into the pours of the casting.
    #8 Cure part at 375 for 25 minutes
    #9 Turn off oven and alow to cool very slowly, maybe crack the door slightly.

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  • tomg552001
    replied
    I found that my best method for curing is to outgas at 375 for 15 minutes, than cure at 410ish. It seems to give me really good results.

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  • dsacco1013
    replied
    tOM, i WAS WONDERING WHAT WAS YOU OUTCOME?... Caps lock

    Dave

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  • DALE
    replied
    If the part is still giving you trouble go down to 325. 25degrees makes alot of difference in cure cycle.

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  • tomg552001
    replied
    Thanks for the info guys. So would say 30 minutes at 350 be good or should i go even lower for a longer period of time? Most of the pieces im powder coating are about the size of the part i mentions before. I do use a in oven thermometer to keep track of temp aswell.

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  • DALE
    replied
    Tom

    Okay first thing, don't waste your time talking to your powder manufacturer for a different formula,as a hobbiest it's not gonna happen.
    Next media blasting is a great way to physically clean the surface you just need to remove blasting residue afterwards.For aluminum soapy water works fine with a clean rinse then dry in oven and outgass at same time.
    Third you can bring most powder cure temps down to 300-325 and add ten min to time, stay above 300 for the whole process. This lower temp should be your ticket to success. Be sure you have a thermometer in oven for accuracy, don't trust knobs they are usually generally set unless you have an industrial oven.

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  • rivermasternc
    replied
    Tom:

    The time/temperature should be OK. Drop the temp a bit if you want to try a longer time. Say 375F for 30 mins. Aluminum is not very tolerant of a lot of thermal processing.

    Handle the parts with cotton gloves after blasting. If they need degreasing, do that before blasting. I would skip the "pretreatment solution", particularly as a last step. If you have some grit material embedding in the surface, knock that off gently with some 320 grit 3M wet/dry abrasive paper (use dry). Try to not sand the blast profile down, you just want to knock that embedded grit out. If no embedded grit, do not sand at all.

    -Scott

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  • tomg552001
    replied
    I was under the understanding that it helped dissolve any surface oils such as from my hands after touching it etc. How are my times and temps? Any suggestions on that?

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  • rivermasternc
    replied
    Why would any "pretreatment solution" be needed for an aluminum substrate if you are grit blasting? I can see a phosphate solution on a steel part to reduce rust creep.

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  • Hemi-T
    replied
    Try coating a similar part without using the pretreatment and see if you get the same results. I would be suspicious of something that says it works for paint and powder coating. They're different beasts. Any contamination could potentially cause outgassing. The brake cleaner I use is extremely volatile, and vaporizes completely in seconds even without heat, but I still preheat to outgas aluminum parts anyway. Good luck!

    Hemi-T

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  • tomg552001
    replied
    Hmm, its something i purchased from columbia coatings. It's a paint/powder coat prep that they sell.

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  • Hemi-T
    replied
    What is "pretreatment solution"? I used brake cleaner (not the orange based stuff) to degrease my aluminum valley cover inside and out, then sandblasted with silica, then baked at 450 degrees for 15 minutes to outgas, then cooled and powder coated as normal. No problems. It has been on a running engine using synthetic oil for 3 years before being powder coated.

    Hemi-T

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