Craftmaster bilge paint over Hammerite primer

[blythecooper]

A passing boater has just told me that Hammerite Red Oxide Primer has to have Hammerite top coat over it. I have Craftmaster Grey Bilge Paint. He think I shouldn't combine the two. What are people's thoughts on this?

[David Mack]

They have different solvents, so you may get an adverse reaction.  Should be fine if the primer has had enough time for the solvent to fully evaporate.

[David Schweizer]

I painted the section between the gunwhale and first guard iron on Helvetia with Craftmaster black over Hammerite red oxide. Circumstances meant that there were several weeks between the two, but it went on fine and demonstrated no ill effects.

[sharpness]

I've used Internationals Pre-Kote & Toplac over Hammerite Red Oxide primer without any problems.

 

Steve

[Mariner]

It's a gamble. In recent years, I have become firmly of the belief that primer and top coat should come from the same source; you have bought a "paint system". However, in most instances, people do get away with random combinations.

 

As for Hammerite, 20 years ago they made really good paint, but as with many brands, they have re-formulated their paints to meet current Health and Safety regs and what sells as Hammerite now is not the same stuff and I don't use it any more. The one exception is that I do use their Special Metals Primer, which is intended for aluminium and various other non-ferrous materials; quite please with that, which seems to be a water-based paint.

[blythecooper]

Well I've tried it.. Will see what happens! Planning on taking up the whole floor (slowly!) because there's water trapped throughout the cabin bilge from a shower leak. Bathroom and gas lockers can be my trial run!

[Dr Bob]

15 minutes ago, Mariner said:

It's a gamble. In recent years, I have become firmly of the belief that primer and top coat should come from the same source; you have bought a "paint system". However, in most instances, people do get away with random combinations.

It's not a gamble. 

Most paint companies want you to buy their system, but it is not needed. Different paints can be applied in the majority of cases providing you follow manufactures instructions on application times,temps, overcoating etc. If you are worried stick to using the same paint chemistry, i.e. Epoxy over epoxy but brand to brand is not important. Solvents aren't an issue if you let the primer dry for the required time. 

[bizzard]

Generally, ordinary oil based paint will go over any other type of paint without reaction, its the other way round that a reaction might happen. Cellulose  or others on top of oil paint for example, although cellulose is not much used anymore, only perhaps on certain classic cars.

[Mariner]

4 hours ago, Dr Bob said:

It's not a gamble. Different paints can be applied in the majority of cases providing you follow manufactures instructions on application times,temps, overcoating etc.

Why did you feel the need to use the term "majority of cases" in your response? If it's not at all a gamble (even a very small gamble), that term is totally superfluous, isn't it?

 

It seems to me that using a system is very probably ( I too can qualify every detail) more likely to achieve a really good outcome than using whatever "falls to hand". A quality company will optimise the primer and the top coat for best compatibility and be fully complementary in providing a protective coating. For critical applications, the system may consist of a number of coats.

 

When you consider all the hard work necessary to do good preparation before painting, I really do want (and I'm willing to pay) for paint which will perform as well as possible. Strangely, a friend who is extremely fussy about only using what he considers to be premium grade (big-name / high cost) engine oil in his car told me the other day that he was painting the underside of it with some paint he bought at Lidl. That seemed like an inconsistent approach to materials procurement.

[Dr Bob]

3 minutes ago, Mariner said:

Why did you feel the need to use the term "majority of cases" in your response? If it's not at all a gamble (even a very small gamble), that term is totally superfluous, isn't it?

 

 

You cannot mix paints in all cases. Some top coats will be incompatible (or not recommended to be used) with certain primers. Hence my use of the words "majority of cases". Understanding what you can and cannot use is therefore not a gamble but a technical judgement. For example, if I used an epoxy primer, I would make sure I got my top coat on between 24 to 48 hours and likely only use and epoxy top coat whereas if it was an 'alkyd' primer, you could put most things on top of it days after. I would not mix coatings with widely differnet flex strengths etc.

In a past life I spent a number of years as tech manager of a coating development group so fully understand the chemistry of coatings. I would have no qualms about buying a good primer from company x and good top coats from company y if the coatings are compatible.......and that's how I am touching the boat up now. For a lot of the external boat steel work (excluding immersion duty) a red lead alkyd paint would be my preference (but at the moment I can only find it in 2.5L tins.....bit big for my touching up this year) and then a good top coat from one of the bit suppliers (International, Jotun etc). I've just gone for a bog standard red oxide primer which should do.

 

15 minutes ago, Mariner said:

 A quality company will optimise the primer and the top coat for best compatibility and be fully complementary in providing a protective coating. For critical applications, the system may consist of a number of coats.
 

Of course they will but many many of the coatings on sale are similar types of  coatings and will work just as well with say other primers. Paint formulation is not rocket science and primers tend to be quite 'low tech'....... high filler content and good surface wetting.

 

If was doing a total repaint then I would use paints from one supplier as then you may have some protection if it falls off 12 months down the line....but that will never be easy as 90% of paint issues are usually down to preparation and following application guidelines to the letter ...and that would be impossible to prove.

[blackrose]

9 hours ago, Mariner said:

 

As for Hammerite, 20 years ago they made really good paint, but as with many brands, they have re-formulated their paints to meet current Health and Safety regs and what sells as Hammerite now is not the same stuff and I don't use it any more. 

I agree. Having painted my engine hole with Vactan followed by 2 coats of Hammerite, I have to say both products are rubbish! 

Edited May 18, 2018 by blackrose

[Richard10002]

2 hours ago, blackrose said:

I agree. Having painted my engine hole with Vactan followed by 2 coats of Hammerite, I have to say both products are rubbish! 

Could it have been one or the other, that caused your opinion, rather than both? What has happened?

[Dr Bob]

4 hours ago, blackrose said:

I agree. Having painted my engine hole with Vactan followed by 2 coats of Hammerite, I have to say both products are rubbish! 

 

1 hour ago, Richard10002 said:

Could it have been one or the other, that caused your opinion, rather than both? What has happened?

Yes, it would be good to hear what went wrong. Can you describe how it has failed. I personally wouldn't use hammerite as it was in the past a very brittle coating and no good for immersion so the engine hole is not the best place for it. I was considering using Vactan this year though.

[WotEver]

I used Vactan followed by Danboline (grey) and it lasted well for me. 

[David Schweizer]

10 hours ago, Dr Bob said:

 

Yes, it would be good to hear what went wrong. Can you describe how it has failed. I personally wouldn't use hammerite as it was in the past a very brittle coating and no good for immersion so the engine hole is not the best place for it. I was considering using Vactan this year though.

When the engine on Helvetia was removed for a re-build, I cleaned out the engine box and gave it two coats of Finnigan's Smoothrite (now known as Hammerite Smooth). which seemed to be less brittle than original Hammerite. I checked with Finnigans regarding it's resistance to heat, water, and oil, and they confirmed that it was suitable for use in close proximity to a diesel engine, and they were correct. Ten years on it was still in pristine condition with no chips or degredation, and very easy to keep clean.

[roland elsdon]

I painted a  rusty milk churn with copper coloured hammerite 20 years ago for my parents. It still sits in the garden, and apart from being dirty, looks as it did.  My triumph spitfire equally rusty was painted in places with the remaining paint. Needless to say the triumph had to have major welding 2 years later.

I used owatrol oil on rust last year on the boat as recommended. I can confirm it does not work. The paint has already bubbled in spots.