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Front discs - to coat or not to coat

Discussion in 'Steering, brakes & Suspension' started by steve_4802, Dec 31, 2016.

  1. steve_4802

    steve_4802 Active Member

    Sunshine Coast
    Perhaps someone has some experience or knowledge with regard to coating brake discs;

    As I'm pulling apart the front end right back to the torsion bars I'm thinking of getting most of the suspension components powder coated up while there; splash guard, steering knuckle, torsion arms etc. Always nice to put it back nicer than I found it.

    I'm unsure, however, if it's ok to powdercoat the hubs and discs. I will machine the pad area of the discs after (as doing new pads anyway) so there wouldn't be any powder coating on the pad contact area, but it's the heat that I'm uncertain of. Might the discs get so hot that the powder coating at the edges and centre be damaged? Ditto for the hub that's in direct contact with the disc?

    Also, might coating the disc in powdercoat or other paint compromise the ability for the brakes to shed heat, and thus reduce braking performance?

    Arent top end brake discs coated anyway?


  2. Wayne murray

    Wayne murray Well-Known Member

    Seven hills
    I wouldn't get brake discs powder coated. One after they are powder coated they are baked at high temp to cure the powder coating.Which I don't know might affect the disc itself or the steel's properties (I could be wrong)Two you would still have to get the paint off the area's that are vital in them working correctly (pad contacts the disc) and also the area where the wheel torques on the disc.
    I have mine painted but I sprayed them and covered the areas that were vital areas as mentioned above.I haven't notice when I painted them if it's affected the braking capacity.
    Powdercoating the splashguard wouldn't matter.
    Any area that needs to be torqued when tightening nuts I wouldn't powdercoat .As to my thinking the powdercoat might affect the torquing of those nuts. Or where the ball joint ,steering knuckles go as they are pressed in or have a taper fit. As I mentioned above does the baking process affect the steels temper .
    I have painted areas you have mentioned but I normally use a spray gun or a spray can and cover vital contact areas.
    I have heard do not get your front beam powder coated as you have bearings inside which get destroyed with the baking process of the powder coating.
    I know top end brakes do the calipers but not to sure if they do discs I assume they would,but I say they would have to stop where the paint goes and how they paint them I also don't know.
  3. cbus

    cbus Well-Known Member

    sunshine coast
    Cant say definitively but would go a high temp paint instead.
    POR 15 also have a high temp range
    Powder is part cured at 180C and full cure 240C.
    (To clarify Waynes qn re disc and heat it doesnt matter.
    Disc operating temps can be much higher than powdercoat bake temp.)
    Disc could exceed that under prolonged downhill use.
    Dont expect the hub would achieve that under any conditions.
    Not on a kombi at least.

    I would second Waynes point on removing powdercoat and thick paint on surfaces that face for nuts.

    If wanting heat disipation ( generaly unecessary for this app in my view) then a very thin coating of flat/ satin black or specific ceramic coatings .
    Prep is very important for heat coatings but except for the disc it isnt realy in that category.
    Heatproof coatings should be as per single coat.
  4. DakDak67

    DakDak67 Active Member

    Yes, paint as above ^^
  5. steve_4802

    steve_4802 Active Member

    Sunshine Coast
    Wow, Very helpful responses, thanks. Based on the above I will completely leave the discs and hubs, mainly for concern of fitup of hub inside disc. If I get really keen I'll go high temp paint as suggested.

    Now moving onto further consideration of other front members which was partly flagged above; steering knuckle, torsion arms, stabiliser bar, and splash guard.

    Paint seems the preferred option but my preference for powdercoat relates to an (expected) improved durability. Every few years when I pull bits of the front end apart I will be rubbing to remove grease/dust etc and the paint may be starting to show signs of deterioration. I worry that I'll more regularly be repainting, especially after degreasing, wire brushing etc as often used on these bits that are very prone to being dirty. I would hope that a black gloss powdercoa would hold up better and will hopefully give many more years of looking sharp, even after being pulled on and off and cleaned a few times.

    So, noting I am now no longer looking to powdercoat discs or hubs; in light of my reasoning above does powdercoating the front suspension components seem ok? I originally thought it was a non issue but now I'm thinking it might also be a questionable move.

    Note that I would request that powder coating not be applied to any tapered connections such as where the steering knuckle receives the tie rod ends or ball joints, or where the hub assembly sits. Ditto for the torsion arms where they sit inside the front beams.

    Does the above seem ok, or are even these parts not well suited to powdercoat?

    Thanks for your further input.

    (Won't be touching the front beam this time around - concern for bearings noted with powdercoat)
  6. Grantus

    Grantus Well-Known Member

    Southern ACT
    My 2 cents worth......

    Powdercoat is a great hard finish, but more brittle than enamel, and will chip easier than enamel.

    I have easy access to powder coating for my bull bars, but still prefer the slightly more flexible enamel finish, for wear and tear, and easy to recoat every 5-8 years when necessary.

    Just my opinion for road use....;)
    steve_4802 likes this.
  7. cbus

    cbus Well-Known Member

    sunshine coast
    A good quality powdercoat and a quality 2pac paint will have similar properties depending on actual selection and application/ prep.

    Good powdercoat such as found on a quality bull bar will have excellent adhesion and chip resistance.
    Poor quality such as chinese furniture will crack and peel within a year or two.
    Depends on powders, cure, prep.
    Done properly it will easily meet your requirements.

    You will need to degrease then blast the components .
    Critical surfaces will need to be protected then masked.
    Essential to have a prime and colour coat.
    Not just a heavy single coat.
    Attention needs to be made to ensure full bake.
    Large mass objects take longer to get up to temp and it might be a temptation to take shortcuts on a mixed load in an oven.
    Powder shops often have parts lying around a few days before getting coated if they are a problem item.
    Rust can develop in this time.

    This just means you need to be confident in the shop and detail what you want done.
    The advantage of powder is primarily time and material savings / quick handling plus durable in a production type environment.

    Paints can be chosen to suit abrasion, chemical resistance, chip resistance, gloss retention under uv.

    Given your desire for elevated performance in coatings I would bypass lacquer and enamels.

    Thorough degrease and sandblast will give best results but not essential
    This ensures clean surface and physical key.
    You can just thoroughly degrease and abrade if desired.
    Treat previously rusty surfaces with phosphoric acid rust treatment and wipe off with damp rag as per instructions.
    I wouldnt use tannic rust converter under epoxy .

    Adhesion depends on paint used and prep standard.
    Ease of clean relates in part at least to smoother shiny surface but again it means a good " full" topcoat rather than panel smooth flat surface.

    Starter pack would be a hit with super etch then engine enamel or similar.
    Both avail aerosols.
    This is likely a bit harder and more resistant than touch up enamel .
    I wouldnt use quick dry enamel.

    Next option is an epoxy mastic 2pac.
    Built to tolerate less than perfect prep and added durability.
    Used for semi trailer chassis etc.
    Doesnt hold full gloss but prob easiest and quite adequate.

    Better version
    Mask and prime with an epoxy zinc primer such as jotun penguard.
    Sand if desired then a second prime or just top coat with colour asap once recoat time allowed.
    Top coat. 2 coats with 2pac polyurethane such as wattyl poly u 400 .
    Or a much better/ harder but flexible jotun imperite.

    You can brush the 2pac' if necessary.
    If spraying, they are much slower drying so allow 1/ 2 hr flash off between sprayed coats.
    If brushing, allow recoat time before second coat. Likely 16 hrs.
    Most can use gp thinners as alternative as genuine thinner very expensive and unnecessary in this application.
    Check some in a small mix first.
    Certainly penguard and poly 400 will.
    Not sure re imperite.
    If incompatible it will curdle quickly.
    If it doesnt curdle its fine.
    Dont try and strain it if it curdles :)

    Once you have the paint it will do a large area for a cost thats prob same as only a couple of small items powdercoated.
    steve_4802 likes this.
  8. steve_4802

    steve_4802 Active Member

    Sunshine Coast
    Fantastic cbus! You got me leaning towards painting.

    Can you recommend any good paint suppliers in Brisbane? I can then sort out final paint system with them. Thinking along the lines of brushed on 2 pack. Spray would be better but for undercarriage bits and pieces it's not worth the trouble as I'm not set up to spray.

    Also chasing someone for sandblasting. Anyone got any recommendations for Brisbane area?

    Appreciate the input on all this. I'm much happier with the direction I'm taking now.
  9. cbus

    cbus Well-Known Member

    sunshine coast
    Any paint shop that stocks industrial or marine should have suitable paints.
    These are much cheaper than auto and good quality.
    Most will have no idea what works.
    Check someone local who stocks croda or wattyl and I can give you details.
    Other brands also ok but I am familar with these.

    I wouldnt blast the spindle as you would need to be careful not to damage machined spindle surface.
    Suggest prep by hand.
    I dont like machine wire brushing as it burnishes rather than clean .
    Degrease, paint strip disc , hand sand or hand wire brush ,clean and acid prep.
    HCl works quicker on rust but you must rinse well with clean water then use phosphoric and rinse again as per instructions.
    If you blast then protect parts with rubber hose firmly clamped.
    Theres a guy in morayfield who does ocasional saturdays on blasting mixed bits for these type of job at a better rate than usual.
    Will check on his details.
    He also does normal blasting
    Otherwise no idea of brissy blasters.

    Check data sheets on any products you want to consider.

    Scroll to bottom of page and download technical data sheet
    Last edited: Jan 2, 2017

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