Chainplates life expectancy

[jibes138]

Amother important process for stainless is to "passivate" the material. This is a chemical process to remove microscopic contaminants from the surface. As the metal is worked with tools microscopic particles of other materials get imbedded in the surface. Passivation chemically removes these contaminants.

 

[Ross]

Amother important process for stainless is to "passivate" the material. This is a chemical process to remove microscopic contaminants from the surface. As the metal is worked with tools microscopic particles of other materials get imbedded in the surface. Passivation chemically removes these contaminants.

We used to used dilute nitric acid.

 

[alexco38]

If I were you, I'll replace them with thicker and wider material. The price of material compare to labor (you time) is minimal.

My simple theory is something needs replacement, why not improve it. Especially for older boats.

 

[jibes138]

Passivation

Passivation is actually a multi-step process starting with cleaning the part, then an acid to remove the contaminanats and then another rinse and then another acid that forms the surface film that provides protect. You can search on passivation of stainless steel on the net and get a description too long to repeat here. It is a standard process and used throughout industry. Don't just go dipping parts in dilute nitric acid without doing the rest of the steps first.

 

[rhythmsurfer]

Good point Ross

 

[RichH]

The choice 'passivation' for chemical service of 300 series stainless is mechanical mirror polishing followed by electropolishing. This results in a 'flatness' of 10 micro-inches and the planar flatness is what gives the better resistance to chemical attack AND fatigue resistance. No nicks, no 'sharp edges', no weld scars, ..... FLAT.

Best of all the DIYer can do 'almost' all this his/herself by using sandpaper, then a high speed buffing wheel and the correct 'white metal' buffing compounds - and simply buffing to a 'mirror-like' finish. Much much better than acid 'passivation'

 

[Roger Long]

Best of all the DIYer can do 'almost' all this his/herself by using sandpaper, then a high speed buffing wheel and the correct 'white metal' buffing compounds - and simply buffing to a 'mirror-like' finish.

Looks like I'll be doing that this winter. I'm having a complete set of new standing rigging made up so it's also time to look at the chainplates:

I see that I missed a bit when I re-bedded the cover plates five years ago so there may be trouble where water has sat in that slot. Fortunately, it's the aft lower which isn't highly stressed.

These boats have a great chainplate design. They don't depend on the bolts at all for strength. With the full length aluminum toe rail above and the large flange distributing load directly into the hull flange, it's a very robust design. (Nuts removed in anticipation of pulling the chainplate out.)

If I do have any problems that require reconstruction, I may have the new ones made up out of bronze.