21SE stainless steel

[Theibis]

I've had my 2007 21SE in the water now for 5 weeks. I noticed today that the stainless steel surrounding one of the rod holders was getting a freckled rust appearance on it. Is this a sign of bad stainless? It will come off with some ss cleaner, but since the boat only has 20 hrs. on her, I thought it was premature to see discoloration.

 

[greatcir]

Oh I can remember my disappointment with my first boat with stainless steel on it. As it began to sort of spot rust, I fussed at the boat salesman. He calmly asked me to say the word stainless very slow. I could finally understand him that it is really stain less but not neverstain. Light maintenance will easily maintain good stainless - clean & add a coat of wax and some compounds do both in one application. ..............Pete

 

[jonas grumby]

I'm no metallurgist but do know that most corrosion-resistant steels (CRES) have iron in thier alloy. The indication of corrision in iron is in the form of rust. This is not an indication that something is wrong w/ your brightwork. On many occasions, I've seen rust on CRES components associated with the most expensive power plants in the world- nuke reactors!

 

[Tjay]

I had one that was much worse than the rest. Take it back. For the money you spent they will replace it. They did for me.

 

[pelagic2530]

On many occasions, I've seen rust on CRES components associated with the most expensive power plants in the world- nuke reactors!

that is SCARY :shock:

 

[Slipstream]

have the same on my new 23se with one of the rod holders. I'll have the dealer look at when I take her in next time. Very minor, but w/ a new boat you expect a lot.

 

[DaleH]

Contrary to popular opinion... stainless steel is neither free from 'stains' nor free from 'rust' or corrosion.

I noticed today that the stainless steel surrounding one of the rod holders was getting a freckled rust appearance on it.

Stainless will discolor is a layer of water is allowed to 'stand' on the metal, as it is the of oxygen that actually prevents SS from rusting. Atually it is from the microscopic layer of iron-chromium oxide within the metal, but you get the idea.

However, if that layer is damaged or is sealed off from 'air', it can corrode. This is also why SS is not recommended for use near or below the waterline. That's when you want naval bronze. This picture below (bolt on the bottom) is a sample of crevice corrosion, where a SS bolt failed to corrosion appearing in an application that kept it wet and without a blanket of good 'ol O2.

But also see the info on 'welding' below. I'd bet that's a welded rod holder ... am I right?

On many occasions, I've seen rust on CRES components associated with the most expensive power plants in the world- nuke reactors!

I wonder if that was near any weld area. When SS is welded, the chromium in the wedlment area is 'burnt off'. To be technical, it is a phenomenon of precipitation of chromium carbide particles along the grain boundaries, which depletes the chromium in the adjacent grains. In layman's terms ... the steel now left behind really isn't SS anymore, at least NOT of the quality the parent billet was as it came from the forge and then as fabricated.

And some SS discolor more than others, as some are not passivated. 304 series is THE most popular for use on a boat, as it is cheaper, but 316, specially 316L, is de bomb for marine use ... when you can find it! It is passivated and had molybdenum in it along with the chromium.

Best ways to keep stainless 'stainless':

* Keep it clean
* Keep it waxed
* Wash off saltwater, even if you don't clean or wax ...

 

[jonas grumby]

That shouldered bolt almost looks like it has been victim to what we call de-alloying. Was used in a pump or moving equipment?
BTW- the corrosion I've seen on certain power plant components is of very-very-very light but naturally occuring amounts. Do not be afraid! We have the best record ever of keeping our plants safe. Now the civilian plants...?