Sacrificial Coatings and Cadmium Bloom

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Protecting metallic components for a long shipment can be difficult. Sea voyages will expose those parts to long periods of highly corrosive salt water. Even if they don’t get wet, the marine environment is very harsh on metal products that have not been properly treated.

Even if you aren’t shipping overseas, metal products that are large might need to be carried in an open air truck bed or train car. This means rain, sun, snow and even road salt can get into these parts, causing corrosion. Parts that are damaged before they ever arrive to a job site or a customer are of no use.

Sacrificial Anodes

One trick that has been employed by marine manufacturers for many years is the use of a sacrificial anode. This is essentially a piece of highly reactive metal that is used to pull all the contaminants towards it and keep them away from your product. In the case of boats, the mechanicals that drive the ship.

Sacrificial anodes can be used in shipping as well. They can either be affixed to larger parts, or be included in boxes with parts. Much like a desiccant, the sacrificial anodes will slowly corrode as they pull the dangerous chemicals out of the environment.

Since they corrode, they will need to be replaced. Typically a visual inspection will be enough to tell when it is time to replace one of these.

Cadmium Coatings as Sacrificial Anodes

An additional method that can be used by some manufacturers of metallic parts is to coat those parts in cadmium. Cadmium is a metal that would go over top of another metal to protect it from corrosion. The most common metals that cadmium coating is used on are:

  • Steel
  • Zinc
  • Aluminum
  • Iron
  • Titanium Alloys

Cadmium is used a lot in marine applications. The coating is particularly resistant to the effects of sea water. Saltwater corrosion is what is called an electro-chemical process and cadmium protects from that very well. Due to it being naturally occurring and relatively light, it also makes a good coating for aerospace parts as well.

Cadmium acts like a sacrificial anode when applied. It pulls the chemicals out of the environment and bonds with them. This prevents them from getting to the protected part underneath keeping it intact and functioning.

Cadmium Bloom

Issues arise when cadmium begins to corrode and develop something called bloom. Bloom is a white chalky substance that will begin to appear on the coating as it begins to corrode. The compounds that bloom is made of are highly toxic and can lead to irreversible lung damage and emphysema. Bloom only occurs when the coatings are mixed with certain chemicals, typically when they are in an environment that is highly acidic and there is little or no ventilation.

If you are interested in using a sacrificial anode to protect your shipment, or other metal protection techniques, Cratex Group can help. Contact us today for your industrial packing needs!