Having battled rust in the bilge of a steel boat for 29 years now I have come to the conclusion that unless you can sand or grit blast the two packs are a waste of effort and money
I did a hull refit
in 2012 and went from one end of the bilge to the other with pneumatic chisels and needle guns
and recoated with epoxy and it is failing in numerous places.
I have used cement render with boiled linseed oil
and white cement for a number of years and have found it to be just as effective as the epoxy coatings and I suspect in some places it has given better performance. I have taken to filling water traps with it and it seems to work fairly well.
I am now coating the bilge with waxoil made out of candles and engine oil
. For the first batch I went with dissolving the wax with white spirits but have given up on that and now just heat the candle wax in a metal bucket and stir in the engine
oil. It appears to do a good job of wetting the steel, can be reflowed using a hot air gun and will be readily removable with solvents should I wish to do so.
I went with the waxoil after reading about it on the forum. On pondering on it I remembered an oil company storage
yard near the sea in south east Asia
where they coated pipes in storage
with waxy crude oil. It was filthy to handle the pipes but the storeman told us that over decades of experience this proved the most effective protection in the long term. Since nothing much else has been very effective I thought I would give it a tryout.