Hot-dip galvanising alternatives

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A. Hi Jefferson. Blackening offers close to no corrosion resistance. Zinc remains the least expensive metal to coat steel with, and galvanizing is the only practical way to get that thickness on steel structures. Electroplated zinc is 1/10 that thick +/-.

Powder coating on top of electrocoating on zinc phosphatized steel might be less expensive, and can be highly corrosion resistant, but it does not offer the degree of sacrificial protection in the case of rough handling, field alterations, etc.

Zinc rich "paint", sometimes called 'cold galvanizing compound' can exhibit good corrosion resistance, but nothing offers the proven protection of hot dip galvanizing.

Luck & Regards,

A. Hi Willie. Zinc electroplating is probably not a good alternative. The plating tends to be only about 10% as thick, for 10% of the corrosion resistance. You can specify plating 2 to 3X as heavy as the usual, and/or of a zinc alloy rather than plain zinc, but its life will not really compare. Plus some of the shapes may not get good even coverage by electroplating.

Regards,

A. Mr. V, Depending on the types of steel you are working with you may want to look at zinc rich primers and polyurethane top coat.

This will provide you with good corrosion resistance and a nice appearance . This type system is used quite extensively here in the states. Best of luck to you.

A. Mr.Willie V,

As an alternative to hot dip galvanising you can use metal spray gun. Zinc in the form of wire is used in the gun. The wire is atomised by using Oxygen and Acetylene gas in the metal spray gun. The equipment required are gas cylinders, metal spray gun and a compressor.

Thanks,

Q. Krishan_K Referring to your guideline as indicated below "As an alternative to hot dip galvanising you can use metal spray gun. Zinc in the form of wire is used in the gun. The wire is atomised by using Oxygen and Acetylene gas in the metal spray gun. The equipment required are gas cylinders, metal spray gun and a compressor."
Sir, can you guide me, in India from where I can resource those equipment & consumables like Zinc wire, related fluxes, etc.
We are planning for augmentation of infrastructural facility of Hot Zinc spray for our in house requirement.

Thanks & regards

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A. Dear Mr. V, depending on the dimensions of your parts a process called "ZN®" could be a solution of your products.

For parts up to 4 m in length which are able to be tumbled "ZN®" is a good alternative to hot dip galvanizing.

It gives a better corrosion resistance than hot dip galvanizing and a very uniform surface with a uniform appearance. It is possible to have the parts coated in three different colours (silver, black, green).

The process is based on a special powder which you put together with the parts into a drum. You heat up the rotating drum and stay on temperature for some time. The result will be a very uniform coating with good corrosion resistance.

The process is very environment friendly as you do not need pickling.
Best regards,

A. You can use the metal spray process to spray Zinc on any steel of any size as compared with the hot dip galvanizing process. I fully understand your problem in transporting large pieces for galvanizing and the costs for the process. You can do the metal spraying at your own place and time and the equipment is portable and handheld and the total cost including a sandblasting machine and the metal spray equipment may not exceed 20K, here in the US.

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A. I will guess that Mothers metal polish has an active chemical ingredient like copper and brass cleaners do. If so, you have etched the zinc coating thus the grey look. Depending on what wax is in the "polish" will control what organic solvent will take it off. You could try "Polishing" it with 1200 grit paper that you can get from a good car or boat paint shop. This will remove some of the zinc and give you a very smooth surface which equals bright. Then use a good grade of car polish -one with no cleaner in it. A carnuba wax would probably work well, but normally is much harder to apply and polish. Plan B is to paint the trailer after you have used a solvent to remove the polish.

Q. Thanks,

There aren't any chemical cleaners?

I would have to sand it?

Joe

A. You can pressure wash off the residue which is at least partially a zinc oxide. The problem will be the surface is now micro etched. This causes the light to be bent in all directions, or an interference with the reflection of light from the surface to your eye. It will always look dull.

A. A stiff wire brush and some 00 steel wool ⇦ this on eBay or Amazon [affil links] will work fine after washing it down to remove what you put on it. The wire brush will make it shine, but will leaves some lighter marks. The steel wool will shine it up. Don't worry about the overall appearance, it will blend in together eventually.

A. In the galvanization process the steel is cleaned and pretreated and fluxed, then dipped into molten zinc which covers the surface. Because the steel is no longer exposed, it doesn't rust. But even if there is a scratch, the zinc is more 'active' than the steel, producing a constant battery action that keeps oxygen from reacting with the steel and rusting it.

The zinc itself can't rust because only iron based metals can rust, and zinc has no iron in it. It can, however, corrode. But under good conditions the corrosion products of zinc form a tight adherent coating which keeps air and water from reaching the underlying zinc, thereby slowing further corrosion. It is not a foolproof system, but under good conditions it can provide decades of protection without maintainance (50, 75, sometimes 100 years) -- probably more than any other metal finish.

A. Hi Peter. The referenced reply describes a proprietary improvement upon the Sherardizing process. You can learn more about Sherardizing on letter 8591, "What is Sherardizing".

This site is made possible for camaraderie and technical information exchange by generous supporting advertisers, and to the extent possible we focus on technical, generic aspects of metal finishing. Apologies for our limitations.

A. In South Africa, Zinc Metal spray equipment is available to people who want an alternative to galvanising and this process is also used to repair galvanising.

Hi again, Willie V. Hi, George.

As already mentioned, sherardizing, zinc-rich primers, and flame spraying are alternatives to hot dip galvanizing. Other alternatives include zinc alloy electroplating, zinc-rich dip-spin coatings, aluminizing, and mechanical plating. The choice often depends not solely on easy availability, but on economy, how thick the zinc must be for your corrosion resistance application, and whether the application parameters are practical for the components which you need to coat. Although there are many alternatives, please also remember that some galvanized coatings are still functioning after 75 and 100 years in service, and there is no accelerated corrosion test capable of proving that newly hatched alternatives will actually last that long.

When people claim that alternatives are equal or better in corrosion resistance, they actually mean they outperform galvanizing in a salt spray chamber. But in reality, most of the corrosion resistance of galvanizing comes from the slow buildup, over years and decades, of glassy and impervious zinc carbonate reaction products on the surface. A salt spray cabinet prevents this essential corrosion protection mechanism. Good luck.

Regards,

A. Zinc spray equipment can be used for corrosion protection of Steel and Cast Iron surfaces. This is as effective as hot dip galvanising but costs much less. Convenience is similar to Spray Painting.

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A. Hi Pernell. Most paint will not hurt galvanizing (exception, keep copper-bearing "bottom paint" away from galvanizing).

The biggest issue in painting galvanized surfaces is getting sufficient adhesion. The phosphoric acid based rust converter ⇦ this on eBay or Amazon [affil links] s should not hurt, and should help. A special self-etching primer made for galvanized surfaces would be best, and can probably be followed with whatever you like. Good luck.

Regards,