Misconceptions In Corrosion – Part 1

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There are many misconceptions and myths around corrosion of metals and corrosion prevention methods or products.

In part 1 we look at some of those ‘’Chinese Whispers’’ that I have encountered throughout the years. 

The Myth: A common misconception is that stainless steel is never affected by corrosion

Fact: All metals can corrode

Some, like pure iron, corrode quickly. Stainless steel, however, which combines iron and other alloys, is slower to corrode and is therefore used more frequently. All small group of metals, called the Noble Metals, are much less reactive than others. It is, however, rarely a question of uniform or general corrosion – pitting or crevice corrosion is far more common, which are a consequence of the passive layer becoming damaged or being prevented from being rebuilt. 

Chloride-rich environments such as seawater, as well as acid environments or elevated temperatures, will always increase the risk of corrosion problems occurring. 

The Myth: Corrosion only occurs in a particular season (Seasonal Corrosion)

Fact: Rust never sleeps or goes away – it may be highlighted in the summer months, however it is still there during the winter seasons. 

Many companies take extra consideration of rust and corrosion in the summer. Heat and humidity during summertime can prove to be detrimental to metal and manufactured parts. Often the winter months do not get the same attention and considerationOn cold days, when warm machined parts are brought outside or left in a cold atmosphere, they can flash rust. This is due to the differences in surface temperature on the surface of the metal and the environmental temperature, cold air cannot hold as much moisture in it as warm airHowever, moisture alone does not cause corrosion, even in winter we have gaseous pollutants in the air – Sulphur, Chlorine, Oxygen, and others that are attacking metal surfaces, causing rust and corrosion.  

Rust never sleeps or goes away. Choosing corrosion protection for all year round gives you confidence that your parts or assets stay rust free always. 

The Myth: Using desiccant will stop corrosion

Fact: A fully saturated desiccant will begin to release moisture back into the air and can increase the corrosion rate of the metal it is intended to protect. 

Desiccant’s function is to draw and retain moisture from the environment by absorbing moisture in the air and preventing it from reacting with the metal surfaceAfter the desiccant has become saturated and reached its capacity to absorb liquid it is important that the desiccant is removed and replaced. A fully saturated desiccant will begin to release moisture back into the air and can increase the corrosion rate of the metal it is intended to protect. 

It is extremely hard to determine when a desiccant is saturated if no indicating change of colour is apparent. Combining a corrosion protection method in conjunction with desiccant to form an integrated solution is the only way to give you confidence of corrosion not taking place 

The Myth: If you cannot see corrosion with the naked eye, then a part or asset is corrosion free

Fact: In most cases the naked eye is sufficient, but sometimes magnification is helpful or required.

Take for example atmospheric corrosion of carbon steel this can take as little as a few hours to form if it is not protected in any way. This corrosion may not be visible to the naked eye however corrosion is taking place and can be determined by magnification. Once corrosion has started this may impede the activities thereafter i.e. plating or coating.   

The Myth: Water based corrosion inhibitors are inferior to solvent based

Fact: This is a completely wrong statement, as the only difference is that water is the carrier instead of the solvent.

You just need to make sure you have a procedure that fully dries the part or asset to remove the water, which can be straight forward in the precision component manufacturing environment.  

Our new product EnviroRinseTM is a water-based corrosion inhibitor using sustainable oils in its formulation, resulting in long term corrosion protectionwith a gentler impact on the environment and safer working conditions for employees. 

The Myth: WD-40 is a rust preventative

Fact: WD-40 is in fact hygroscopic and will attract more moisture to metal surfaces, which will result in rust.

The Myth: All VCI packaging material is the same quality

Fact: It’s understandable to have different quality levels, but do not expect a cheap costing VCI solution to give you superior corrosion protection.

This is one of the most used terms I have come across and is a misconception. You see VCI packaging and chemicals from online e-commerce to eBay advertising from a wide price range. It’s understandable to have different quality levels but do not expect a cheap costing VCI solution to give you superior corrosion protection. Most of the time corrosion problems can be as a direct result of a purchasing cost save, just because items are labelled VCI it does not mean they all contain the same amount of VCI. This is especially the case in polyethylene packaging as it can range from 1% to 12% VCI content. 

We work with the world leader Cortec Corporation as their UK partner and they ensure quality of the VpCI® range which is patented. When you see the VpCI® brand you know it is of the highest quality. 

Get in touch – it would be great to hear any misconceptions you have come across or even any conceptions you may have and would like clarification on.

Part 2 coming soon. 

Written by Corrosion Expert, Dean Kenny
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