Cathodic Protection at Home

Are your window grills by any chance either underwater, or buried?

As far as I know, cathodic protection only works in situations where the metal to be protected is either buried, or submerged in water (whether "freshwater", or "marine").

Cathodic protection works well for buried pipelines, steel storage tanks, ship's hulls, and even for offshore oil drilling platforms, because the metal structures being protected and the Galvanic (sacrificial) anode are electrically connected to each other in an electrolyte (e.g., saturated soil or seawater).

If, indeed your grills are in one of these situations, you would then have to figure out what to make your sacrificial anodes out of. You would have to form your anodes out of a metal or alloy that is more "electrically active" (that is, possessing a more negative electrochemical potential) compared to the metal in your window grills.

If you are dealing with steel grills, this wouldn't be difficult; but window grills of Mg-Al alloys might be tougher to work out, and the anodes might end up costing more than the epoxy!

Remember, by definition, the anodes are sacrificed, and have to be replaced periodically...

Has the correct priming paint been used?

If the frames are steel, have they been passivated prior to painting? "Jenolite" car-body rust treatment is basically phosphoric acid, and it forms a barrier of iron phosphates that inhibit further corrosion.

u-PVC is becoming a very popular material for window frames in modern home construction locally, it being practically maintenance-free. In some cases, replacement can enhance the perceived value of the building on that basis alone, as well as enhancing appearance. Check local planning regulations before embarking on replacements as there are restrictions in some areas.

My dad used to use mordant solution, I have no idea what it is but I still have a bottle in the garage, it is translucent blue. He used it on galvanized lampposts prior to priming, otherwise the paint would peel. Some window frames are aluminium, but when that starts to go it bubbles which doesn't match your description, (I have no idea what to do about Al). I too, have moved to uPVC.

Preparation is the key, whatever paint you use it must have a good surface to adhere to.

Its a combination of things but generally it would be classified as a week acid. The process you refer to is known as pickling. In order for the paint to stick to the galvanize you first need to remove the (zinc) oxide that had formed on the surface. The acid (sometimes a dilute Muriatic) will remove the oxide and allow the paint to adhere to the surface of the galvanize not the loosely attached zinc oxide on its surface. Some of the old timers would use vinegar for this process, hence the term pickling.

Marine Equipment stores are the best to get the right pretreatment / primer / paint.

After you heeded the advice given in the notes before me.

I have seen a device advertised on a car show on TV that was hooked up to a car body to prevent rust when a car was in storage. I think it was hooked up to the car battery but used the car body as the hot lead instead of as the ground. If I can find the info I will post it here.

Hi Redman46

These devices have been thoroughly debunked, and some companies that sold these devices were under investigation by the authorities. If I recall correctly one company was required to return money to any person who could prove they purchased a device from them and were banned from selling that device or similar devices.

Here at the Canada Centre for Inland Waters for submersion of aluminium in fresh water or soil around fresh water we use magnesium anodes. For submersion of aluminium in salt water or soil around salt water we use zinc anodes.

For protection of aluminium products that will be subject to the weather and not submerged, typically we have the items anodized, either coloured or clear depending upon the application. Occasionally we use hard anodizing if the components will see abrasive or wear related service.

Cheers

mechtech

no you can't... as someone as explained very well cathodic protection works only if there is an electrical conductive paths (soil or water) between the object to be protected and the galvanic anodes (sacrificial of impressed current).... Paint is the perfect options for corrosion control in your case..

look at this documents for more info on cathodic protection

http://resource.npl.co.uk/docs/science_technology/materials/life_management_of_materials/publications/online_guides/pdf/cathodic_protection_in_practise.pdf

http://resource.npl.co.uk/docs/science_technology/materials/life_management_of_materials/publications/online_guides/pdf/cathodic_protection.pdf

and these for the coating.

http://resource.npl.co.uk/docs/science_technology/materials/life_management_of_materials/publications/online_guides/pdf/surface_coating.pdf

hope this helps

S.

http://www.corrosionist.com

See if this site gives you any help.

http://www.nace.org/nace/content/education/Certification/cp/CPIndex.asp

Sacrificial cathodes won't protect your window grills from the effects of UV radiation, which can also degrade paint.

I dont know where you looked for epoxy paint, but I have had incredibly good luck with POR-15 products. Its cheaper then imron and you can buy it at just about any autobody supply store. I painted the frame of my vintage muscle car with it and left it to sit outdoors unprotected for a few years. It still looks as good as the day it went on, without a spec of rust, even with the abundance of salt present from living in the northeast US and being exposed all winter. The stuff is hard too. I painted some goalie nets with primer, rustoleum paint, and then the clearcoat (I believe its called glisten PC) in the POR-15 product family and the nets still look great except where the players skates have gouged them down to the metal. BUt the rest of them have held up to 70+ MPH slapshots without peeling or flaking. A pint of the stuff runs about $27/pint, but you get alot of coverage out of one pint (One pint for me did 4 NHL standard sized goalie nets, single coat, ~3 pints did the entire frame and suspension on my '72 El Camino, 2 coats). You can order the stuff online too.

If the grills you are referring to are outdoor widow or door grills exposed to repeated contact to rain/dry/rain cycles, etc, then the contaminants build up on the surface each cycle and concentrate on the surface. The more frequent the wet/dry cycle the greater the chance to corrode. Also, the more polluted the atmosphere or closer you are to the shore of an ocean (eg) the greater the chance of chloride or sulfate contaminants in the air and their ability to be dissolved in the rainwater. Once the corrosion begins (through any surface discontinuity), the greater is the probability that it will accelerate. Painting (or providing another continuous barrier coating) is generally the most cost effective means to prevent corrosion. Although corrosion on a surface always occurs by electrical transfer of ions dislocating metallic crystals from the surface, cathodic protection is used primarily for situations where the surface is completely and continuously immersed in an aqueous solution.

Take them off and have a professional sandblast them and then have them dipped in hot galvanize. Make sure the coating does not get damaged when you replace them back on the house....

Some people like a quick release mechanism in case of a fire and you need to get out through that window. The mechanism must of course not be accessible from outside!!

I prefer a good burglar alarm with fire detection built in!!

What color do you paint them? There are etching products that could eliminate the need of paint by causing a surface condition that inhibits corrosion.

Powder coating gets high marks too.