Paint

[derek]

Which is considered to be the best durable finish.
Stove enamel: I have found the modern stoving is brittle and chips very easily.
Powder coat: I have no experience, but have been told that moisture can get between coating and surface metal, with obvious corrosion
Two pack: So far this seems to be the best.

 

[John Appleton]

Which is considered to be the best durable finish.
.

Hi Derek , powder coat is a good finish for areas which are fairly inaccessible , such as rear frame , but not for areas such as the tank . It is possible to have powder coat done cheaply , but I would advise shopping around to find the best spec. rather than the cheapest price . We have a local company which has done good work for us , the biggest difference with their work apparently is in the type of primer they use , which eliminates moisture ingress . I have no expertise in this type of coating , just experience of cheap and expensive contractors .
John

 

[timetraveller]

Moisture under powder coating? I don't think so. I have had lots of powder coating done over the years on non motorcyle parts, typically mild steel but also including 150 year old cast iron, aluminium and stainless steel. The part is 'grit' blasted first and then heated in an oven before the powder is electrostatically sprayed onto the part. I do not know the temperature at this stage but you would not be happy to touch it. After the layer of powder is applied the item is then put back into the oven and heated so that the powder melts and flows. Not just solid colours are available but also finishes such as antique gold or beaten bronze. It is possible to get a concours finish but the chaps who do my work generally end up with either some orange peel or imperfections due to blasting grit floating about in the air of the spraying booth. To find out if the finish is durable enough for your purposes arrange to have a small sample coated and when it has cooled hit it with a ball 'pain' hammer. (Pain is what you will experience if you hit it with a hammer without prior agreement.) I find it very durable. For parts subject to regular wear, eg sides of petrol tanks, a two pack polyurathene should be more abrasion resistance but I use two pack acrylic and that lasts for years. Years ago I did some sidecar racing and the guys involved in that would not use powder coat as it is so tough that they could not see cracks developing in their frames!!

 

[nkt267]

[QUOTE I do not know the temperature at this stage but you would not be happy to touch it.][/QUOTE]
The man who does my powder coating(bring it back and I'll re-do it if you're not happy)says the temperature is 400 degrees,it is hot enough to melt out body filler so you can't prep the job that way.

 

[greg burt]

Two Pack
The whole Bike

 

[Ken Tidswell]

two pack paint jobs

The problem with 2 pack is the undercoat, Zinc oxide appears to be an industrial favourite. However it is soft and does not provide agood key, particularly when put on too thickly . It is sensitive to chipping which reveals the grey coating underneath. My experience with powder
coating which is a hot melt process, is that the coaters suffer from the PPO syndrome. When melted it looks a like badly dipped paint job. It can be rather brittle so that slight adjustment say of the ends of mudguard stays can produce cracks. If put on too thickly it looks like the bark on a tree, and is dangerous on the mating surfaces of brake drums.
Under pressure it flows and a drum, if it is a rear drum ,will come loose. i have seen this happen in Canada. The Pinchin Johnson No 2 cycle finish was very good and some machines still retain their coatings after 60 years. I speak from poor experience of all the above post P-J.

 

[timetraveller]

The problem is Mr Boggler, Sir, that there is not just one type of undercoat. eg , acid, acid free, etching, non etching, chromate and so on. I am no expert on this but I do know a club member who is. If I can contact him then I will post what information I can from a reliable source. (He does not work on Vincents for a living and so is bias free.) If I remember correctly then when I started to use two pack acrylic I asked his advice and was told to use a chromate free non etching primer on old tanks where there might be some residual rust after all the rubbing down etc. Always remember that there are people out there wanting to sell you their products who will give you professional advice. The main problem is to find the ones who know what they are talking about and not just trying to sell you what they have in stock. The other note of warning is that there is not just one type of 'two pack'. Acrylic and polyurathene are just two I have used and you can be sure that there will be others. I use acrylic on my bikes and used to use two pack polyurathene on my boat. However, I have found that for my use one pack polyurathene lasts better on boats in the Med.

 

[Comet]

I am not an expert by any means on paint systems, but I do sell Polyester powder coated gutter systems. Powder coat if done correctly is very durable. Our manufacturers offer a 20year guarantee against corrosion. I have also seen powder coated ally being hit with a ball pein hammer so that it has severe denting and the coating does not chip crack or break away. But the key point being "if done correctly". It can also be supplied matt, semi gloss or high gloss. But it is generally obvious that the finish is PPC and not 2 pack or Cellulose etc.

 

[timetraveller]

OK Chaps, I finally met up with my chum who is the paint expert and it seems that the required primer is Chromate etching primer. This should be applied to bare metal which has been cleaned as well as possible and this primer should help to get rid of microscopic bits of rust which might have been missed and will also provide a good key for the primer/filler which will need to go on next.

On the subject of water under powder coat; I was looking through the specs of some that was used on a rebuild and modernisation of an old telescope (two tons weight and 14 feet long for those who wonder about such things) and I noted that the specification for the powder is 10 minutes at 200ºC. Have a nice day

 

[clevtrev]

Chromate is never used on bare steel. Only on plated steel surfaces. Used for aluminium, but chromate is now BANNED.
Steel is normally phosphated.