Log in
Article search:

Q & A

what is the best hull blacking product

What is the best hull blacking product for steel bottom wide beam . What is the easiest for applying and quickest drying time. I have read that B&Q black paint is effective and cheap. Is this true of a boat in a marina in brackish water?

Asked by: val smith  | 11.23am, Monday 13 July

WW says:

Hull blacking tends to come in several forms- though B&Q own black paint is probably not a normal choice- depending on its make-up.
The cheapest blacking is basic bitumen- though it is least likely to stay put on steel- and several coats are needed.
Next up are modified coal tars, which have additional materials (vinyl compounds) which make them easier to apply and also stick better.
top of the range are two-pack hull paints, which form a very strong bond to the hull, as well as being very abrasion resistant, so can last a long time before needing to be coated. however, they do need the surface to be taken back too bare metal, ideally by grit blasting to SA2.5 standard.
The better the steelwork condition, the better the paint will stick. If you are overcoating, you need to establish that the previous paint scheme is both adhering to the steel well, is thoroughly cleaned (with high pressure jets as a minimum) and also is compatible with the paint type you are going to use- a patch test is suggested- for instance, some vinyl tars will dissolve a base bitumen coat, leading to loss of both paint layers.
Typical DIY store paints don't tend to be suitable for boats that are immersed in water constantly- but more for surface protection of exterior steel on land. Underwater, they may blister and fail prematurely. You would be best using marine paints.
Also, depending on the salinity of the water your boat is based on, you may need to consider either aluminium or zinc sacrificial anodes- if freshwater magnesium ones are fitted, they will likely react and dissolve within a few weeks or months! You should be able to get advice from anode manufacturers depending on where you are based.
Please let us know if you need more information

Mark Langley  | 1.34PM, Monday 13 July

If you have two-pack on already, then you should be able to put a single coat on quite quickly- as long as the surface is prepared well (lightly abraded- pressure wash might be enough-doesn't need to go back to steel) it should be fine.
If you know the original two-pack used, they should be able to advise.
Would be a shame to cover two-pack with low-cost bitumen, as you probably would loose the top coating very quickly (it wont adhere very well) and vinyl modified tars won't do much better.

Mark Langley  | 2.21PM, Monday 13 July

Since you have such a short time for the blacking, you would do best to use 2 pack paint. Ordinary paint needs 48hrs to dry thoroughly before putting back in the water, 2 pack paint hardens by chemical reaction and will continue hardening under water.

Rupert Smedley  | 2.36PM, Monday 13 July

Readers say:

Thank you Mark. My anodes are aluminum and will be replaced with aluminum.The hull when built was shot blasted and two pack was used - I'm looking for a cheaper and quicker but suitable method to go over the two pack.
I only have three days for the blacking including the drying.

val smith  | 2.07PM, Monday 13 July

You must log in to post an answer.