Mazda Rotary Club

Hi all,

I have had Black Diamond discs fitted on my FD since December.

One of the main reasons for purchasing was that I had read they have a unique black phosphate coating that prevents areas of non-friction from corroding. Mine have been rusty since about a week after I had them fitted.

I have spoken to Clive at Shy Auto (thanks Clive) where I got them from and he was surprised to hear this, and got straight onto Black Diamond. They told him that there was no guarantee as to the effectiveness of the coating. I have also spoken to the MD of Black Diamond (Chris Hulse) who maintains the coating is a USP for them over other manufacturers, but hasn\'t explained for what reason.

Looking around the web and magazines, I found the following;

Demon Tweeks quotes the following in their catalogue;

"Black Diamond brake discs are made to the most exacting standards using computer aided design. The unique black phosphate finish keeps the non-contact areas of the disc free from corrosion."

Elk parts quote the following on their website (http://www.elkparts.co.uk/product_info.php/products_id/415);

" High quality and fantastic value, award winning Black Diamond performance brake discs are Zinc Phosphate coated, offering long term corrosion protection to non-contact areas."

Candenterprises quote the following on their website (http://www.candrenterprises.co.uk/black_diamond_prices.htm);

" As the name suggests, Black Diamond discs are black in colour. This is achieved by the use of a black phosphate coating helping to protect the discs against corrosion and maintaining their smart appearance."

Chris Hulse says that this is perception and he can\'t be held responsible for what other people say. My only option is apparently to wire brush the discs down, and paint them with heat proof paint - or to send the discs back and he will re-dip them with about a 3 week turnaround, but with no guarantee of them not rusting within 24 hours of reinstalling them.

I am now wondering if other owners have a similar problem and were under the assumption that BD discs are coated to avoid corrosion.

I\'d like to thank Clive at Shy as he was a star and really went out of his way to try and get some resolution from BD.

Cheers, Craig

I\'ll have a look at mine tonight and get back to you!  I think they might be showing some signs of rust though...

i will check mine out tonight also

I had Black Diamond on my car for approx 2-3 years, did approx 25k miles on them.
I have never noticed them rusting, but then have never looked, I have noticed rusting on shiny face but 100 yds up road they would be clean again on first contact with pads.

This is more on the centre bell and in the grooves/drill holes that it is very apparent.

As per g11ary\'s post, the main friction surface is clean as soon as the wheels turn, it\'s just when parked the rest of the discs look a right mess.

Cheers for the replies so far

Black Diamond have never sold there disc to me as rust proof, if they have it in the litrature, Im not aware of it.
I have several manufacturers discs on my site and would not put my hand on my heart and tell a customer they wont rust, they are made from cast iron, and the only way to stop cast from rusting is to enamel, enamel is coated to the surface and is then baked on, the pours of the enamel open is even if it chips it wont rust, just like a bath. But then I dont know the feasabliity of doing this to a surface that takes extreme heat.
Not fighting anyones corner, but they are also the cheapest on the performance market, so possibly not perfect, but do stop your car well.

Just a quick read and although it is not black diamind quoting it, it does say helping protect, which tech is what its doing. Not garenteeing.
It a problem with all open wheels, I guess. Maybe better keeping them painted, or do what I do, dont wash them, let the brake dust build up a nice think black layer. LOL.  ;)

Got my BD\'s about 2 years ago, the guy I bought them from said that they will rust after time . Even with the coating all too do with the high temp\'s generated under braking. So before we fitted them we paited them with black brake caliper paint first. They still look as good as new around the hub area.
Think the only option would be too rub them down and then paint them, lot\'s of hassle but worth it in the long run......cheers Leigh.

Brake discs are cast steel not cast iron ... two very different materials. Black phosphate is a rust inhibitor, in the kind of conditions a brake disc can see I wouldn\'t expect it to last very long. IMHO its a gimmick to sell discs because they look cool in the photos in the catalouge

QuoteOriginally posted by MikeLMR
Brake discs are cast steel not cast iron ..

Yeah sorry, did realise that just used the wrong word, you wouldnt pick them up if cast, same principle applies for baking & baths.

Had a look at mine and the \'Non contact area\'s are rust free,
Fitted on the front using \'Black Diamond \' pads last Sept.
Note: the car didn\'t go out much in the winter all that
corrosive salt on the roads (yuk).
I would (will) expect the finish to last 1-2 years though.
Any help? prob. not
Paul..

yeah i painted the centres of my BD rear discs straight away with "zinc ally" paint as recommended to me by a car savy friend & they still look mint & shiny, fronts i only recently got round to doing & they were at best dull just from brake dust if not a little on the rusty side a quick scrub with wire brush & a bit of the ole abrasive paper give it a spray (yes i masked off the main breaking area before i get labelled with my usual technical retard tag (http://instagiber.net/smiliesdotcom/contrib/drowned/dork.gif) lol) & jobs a good un looks sweet now & i have no fears of rust, was just having a look & realised i didnt have any great pix of it before & i\'ll have to get some of the after at some point if it\'s any use to you?
Si
PS got mine from http://www.decoratingdirect.co.uk/viewprod/s/SIRZINALUS/ (http://www.decoratingdirect.co.uk/viewprod/s/SIRZINALUS/) & (pulp fiction mode on) this **** here sells itself (http://www.greenleafbookshop.co.uk/images/pulp-fiction.gif)

best pikky i\'ve got at the minute where you can just make out the difference is by comparing front against the rear brakes:
(http://img.photobucket.com/albums/v44/scooby_si/Image08smaller.jpg)
Si
PS sub section 24b the paint does not come with the armed response unit attachment lol

PS think i\'m guna use it on me exhaust too after i\'ve got the small amount of rust off the one i\'m goint to eventually sell.........how hot do exhausts get?
Si

Thanks guys - it is disappointing that I\'ve had no real window where the rust was inhibited, but pretty much immediate corrosion.

Ho hum, I have got a tin of the high temp paint, so I guess it\'s out with the wire brush.

Thanks for the feedback,

Craig

Had a look at mine - hard to tell under the layers of dust!  Possibly a bit browney but not too bad!

Will probably paint them black if I can find some suitable paint though.