Rusty the Junk - Paint

So lets just nip down to the local DIY store, buy a few gallons of white emulsion and slap it on all over.
Funnily enough it's not quite as straight forward as that when you want to paint a steel yacht.

Of all the subjects we've needed to investigate in the course of building this boat, paint has been the most intractable. We couldn't find an introductory text anywhere, so any discussions beyond "our paint is best" just resulted in techno-babble until we'd at least worked out the basic terminology. And still, every time we speak to an expert we discover we've missed something, or there are extra factors to take into account, or occasionally a whole new concept. For instance, we'd been asking questions for 2 years before we suddenly came across the idea that too much paint was a problem. So obviously there are no guarantees with this information. But it does give some basic vocabulary and concepts, so there is at least a chance of working out the questions to ask. And of understanding the answers.

A good explanation of paint, Although the terms used are probably American.

We have made a 'glossary' of the terms that we have learnt. But please note that these that are correct in the UK, or possibly just the bit of the UK where we were, i.e. East Anglia.

This glossary gives the primary functions of the main paint types, but this is only part of the story. The paint system as a whole works on more levels than that, so unless one understands all the effects it is best to stick to one system.

Prior to painting the steel has to be prepared. Then there is actually applying the paint.

Peter Millner of our local paint manufacturer, Witham Oil & Paint was immensely helpful and patient while we were struggling to understand the complexities of paint – most of the information in these pages comes from them.

Rust

Rust is a vital part of the preparation of a steel hull. It has three major benefits:

• It removes the mill scale A surface layer of ferric oxide (Fe3O4) that forms on steel or iron during hot rolling. that is always present on sheets of steel as they are bought.
  
• It hardens the surface of the steel. (Note car engine blocks are always allowed to rust before final preparation.)
  
• It leaves a roughened surface to act as a key for paint systems.

Unfortunately it does have a drawback. If you let it go on too long, it becomes very difficult to get a clean weld, without grinding the surfaces back for hours.

We let the rusting process continue for several years as we worked on the boat, but after a while we felt that it had gone far enough. We got quotes from several blasters to come and clean the hull, and eventually went for one that seemed a good price. The lads came, set up everything and off they went. It was all good until they realised that they had to do inside the keel as well.
"Oh! We didn't think that was part of the boat."
After some "discussion", we convinced them that the keel was included in the quote and with much pain and grief they finished the job.
As a last step we had them spray a coat of weldable primer over it all. This holds the rust at bay quite well, but allows welding to take place.

Once we had largely finished welding (you can never be absolutely certain, but you have to draw a line somewhere) we tried to make all the holes that we would need. Obviously the windows and hatches. We tried to put lots of holes through stringers and frames, ready for head linings and furniture etc. You can't work them all out, but the swarf from holes drilled after painting is very hard to completely clean up and rusts instantly.
Then we were ready for the painting.

There are obviously numerous decisions that have to be made with regard to the painting. These are based on highly personal criteria which I suspect a lot of people won't share. That's how it is.

There are several generic steps to painting:

1. Get the boat under cover, either inside a shed or under a tent. Rain and dust give you no chance of a good result.
2. Blast the boat either wet or dry, so as to remove the majority of the rust.
3. Clean the boat, i.e. remove the residue from the blasting, this may cause 'gingering' a very orange instant rust , however this is not usually considered a problem.
4. Do stripe coatsa layer of paint rollered over all the edges and protrusions, over all the difficult parts.
5. Spray the boat inside and out, the appropriate number of times, with the appropriate paints.
6. Bring the boat out into the open, to thunderous applause.
7. Have a huge party.

The final decisions were:

• Use a complete system from Sigma Coatings. This consisted of:

  Inside

  1. Sigma Primer
  2. 2 coats of High Build undercoat second one with thermilate
  3. 1 coat of topcoat (actually we finished up with 2 coats, as the undercoat showed through the first coat. This was the painters' mistake, so they paid)

  Outside

  1. Sigma Primer
  2. 2 coats of High Build undercoat second one with thermilate
  3. 1 coat of topcoat above the waterline
  4. 1 waterproof tie coat To allow the antifouling to bond later below the waterline

• Pressure wash her to remove salt residue from floods.
• Erect a tent over scaffolding on site. Use professional scaffolders.
• Have her grit blasted. Use professional blasters
• Have her professionally sprayed. By the blasters above
• Add the pretty red highlights. Thanks to Big Dan and Jo and Holly.
• Have a big party.