Firstly, SST is an Alloy of several different metals. The key ingrediant to corrosion protection is Chromiuim which produces an gassious oxide on it's surface from contact with oxygen. That layer then stops the oxygen from contacting the chromium and further oxidising it.
There are many different types of SST, with 304 and 316 being the most common that us boaties will come across and the main difference between them is the Nickle content in the steel.
Intense heat will change the Alloy structure within the SST "mix" of metals. Welding is one of those heat sources. The change in the molecular structure of the SST when it is welded can cause an area of "dissimilar metal". This is the same as any situation on a
boat where you have dissimilar metals touching. The result is galvanic corrosion. In SST, this area of metal difference is very thin. So a corrosion called crevice corrosion starts to occur. This creates a "crack" between the the Parent metal and the Weld metal. The crack can be microscopic and the only time you find out it is there, is when the metal finally breaks apart.
A one piece cast SST item is close to bullet proof. The Bruce anchor in SST is one of those that can be trusted. They are cast as a one piece item. Ploughs are another that can be trusted, as their two main
parts are often poured as one piece. The spade design (if available in SST" would probably be OK, as the two sections are bolted and the bolts are no intergral in keeping the two sections together. The ones that are not so trust worthy are any that have the shank and the fluke welded to each other and where that main source of strain is seen across the weld like that. Now ion saying that, several factors can be applied that will make these area's of possible failure a little less possible. Carefully and properly laid welds that have deep penatration and multiples of those welds. This results in the contact area of Weld and parent metal being broken up. One giant weld, although looking great, would have one contact area. The weld needs to be carfully Passivated, ground and polished. The polishing results in a high concentration of the harder Chrome coming to the surface. It also removes the fine scratch marks where crevice corrosion can start working from. And finally, an anchor is usually made from a fairly heavy lump of materials. It would take a great deal of time to
work all the way through to the point of failing. Plus to add to that, the anchor is not a permanant
mooring. It doesn't sit in
Salt water all the time. Hopefully a great deal of the time it is going to sit up on the bow.
So to sum up, I am happy with my shiney SST anchor and I trust it. It is light weight for it's size which has made an enormous benifit with the way the bow rides up. Plus it means I can now carry mor chain because of the wieght saving. I would trust any production anchor. They look good on the bow. As long as you inspect the anchor on occasions, you shoudl be fine. You should be inspecting your anchor, chain, and
winch once a year anyway.
Linear Mode
Recent Discussions