How to Protect Aluminum?

justsomeguy · Apr 22, 2013

You could wax the heck outta them, and often, I think.

But aluminum sort of protects itself by the formation of aluminum oxide...

alexco38 · Apr 22, 2013

You can get them anodized. Some shop do small job.

kloudie1 · Apr 22, 2013

Find a shop that does powdercoat .. bring all the cleats in at the same time for the best price. It involves coating the part with a plastic powder by electrostatic attraction .. then baking the part in an oven to melt the powder into a uniform coating.. very tough .. downside is that it can be chipped if someone hits the cleat with something like a winch handle..

Steve Dion · Apr 22, 2013

They have only lasted for 20 years, I would consider seeing if the mfg will cover them under warranty

Steve Dion · Apr 22, 2013

Maybe it would be cheaper to replace them.

Chris Patterson · Apr 22, 2013

I'd second the powder coat. Tough stuff.

jibes138 · Apr 23, 2013

FourPoints said:
Why would I replace them? They are solid and look great now, I just want to keep them looking good...

They need to be anodized. The wire brush I assume was made of steel wire? At a microscopic level you have contaminated the base metal of the cleat and they will corrode rapidly. Part of the anodize process is to remove contaminants from the surface and then create a relatively hard protective coating on the surface. Without this treatment and in the presence of salt water they will corrode fast. Aluminum is a highly reactive metal (that's why it is such a good conductor) so do the right thing and get them in a shop and anodized.

Bob J. · Apr 23, 2013

Brian,

How did you get the screws/bolts out? Any fastener thru an aluminum cleat or chock on my boat was so corroided in place I ended up drilling them out.

jibes138 · Apr 23, 2013

Stainless

FourPoints said:
The brush I used was Stainless, I would never use a steel wire brush anywhere near a boat (unless cleaning an iron keel, which I don't have)

The proper name for stainless is Corrosion Resistant Steel (CRES). It is steel with a bunch of chromium and nickel that give it the low corrosion properties. But it is still 65% iron. Again at a microscopic level some atoms of iron will likely be imbedded into the surface creating sites where corrosion will be accelerated. Part of anodizing is to remove this surface contamination. Just like in passivating stainless steel imbedded contaminants must be removed first. Abrading the surface with a non ferric (iron) material should physically remove the contamination, something like a scothbrite brush or a nylon abrasive brush.

Coat the screws with zinc chromate primer to protect the interface from corrosion when you install them. This is pretty standard in aerospace when they install helical coil inserts into aluminum housings, the inserts are typically coated with primer at installation.

Most metals don't want to be in pure metallic form (except gold, etc.) and are created by taking ore and freeing up the iron or aluminum atoms by breaking the bonds under high temperature. So metals are in a high energy state and they are doing everything they can to get back to the nice low energy state that they reside in the natural environment. Anodize, passivation, chromating, etc. help slow this tendency to return to a low energy state. I used to explain to folks, take a walk in the woods, how much metal do you see?
Anodize won't cost much, they can throw it in with other work getting done at the same time. Just find a plating shop near you and they should help you out.

316 stainless steel (annealed condition)Minimum PropertiesUltimate Tensile Strength, psi89,900Yield Strength, psi60,200Elongation45%Rockwell HardnessB91ChemistryIron (Fe)65%Carbon (C)0.08% maxChrome (Cr)17%Manganese (Mn)2%Molybdenum (Mo)2.5%Nickel (Ni)12%Phosphorus (P)0.045%Sulphur (S)0.03% minSilicon (Si)1%

Maine Sail · Apr 23, 2013

jibes138 said:
They need to be anodized. The wire brush I assume was made of steel wire? At a microscopic level you have contaminated the base metal of the cleat and they will corrode rapidly. Part of the anodize process is to remove contaminants from the surface and then create a relatively hard protective coating on the surface. Without this treatment and in the presence of salt water they will corrode fast. Aluminum is a highly reactive metal (that's why it is such a good conductor) so do the right thing and get them in a shop and anodized.

Agree 100%. Powder coating, compared to anodizing, holds up quite poorly in the marine environment. We have thousands of Edson pedestals & radar poles out there that show why...

My local shop has a $55.00 min anodizing charge. I can usually save up and get 5 or 6 small items done for the $55.00...

Bob S · Apr 23, 2013

If you do have anodized have them hard coated (Type III anodizing). My plater claims it's better for marine environments. It will change their color to black or dark grey.

Jibes, I was curious why the wet installed Helicoils. Thanks.

kloudie1 · Apr 23, 2013

Yep, you are right, Maine.. Kinda seems like it always starts at a joint between two parts on the pedestals?.. I figured since this is one piece, it would be an easier-to-find service compared to anodizing.. ..

jibes138 · Apr 23, 2013

prevent galvanic corrosion. the zinc chromate primer acts to insulate the dissimilar metals. in reality I question the validity as when the screw is torqued it probably rubs off the coating where the threads are making contact. But it keeps water and air out of the joint so it adds some protection.