Why Does Stainless Steel Go Rusty?
When customers contact us at BS Stainless Ltd they want to know the specifics concerning our stainless steel products because they have had bad experiences in the past which has resulted in them wanting to know one answer to the question of “Why does stainless steel go rusty?”
Many of the stainless steel products which you see in the market work just as they have been intended to however; there are a rising number of instances whereby the end user has been highly disappointed by the performance of the material and in the majority of cases this is because they were expecting something completely resistant to corrosion.
BS Stainless Ltd would like to talk customers through exactly what factors could affect the performance of stainless steel.
Surface Finishes and Stainless Steel
Surface finishes applied to stainless steel can be a major problem and some can cause problems. Stainless steel which has a polished finish will provide maximum resistance to corrosion whereas a directional polish usually produced using silicon carbide abrasives (SiC) will probably only give adequate corrosion resistance when severe environmental factors are against it.
A common surface finish normally achieved with 240 grit alumina abrasives will prove to be inadequate in urban and costal environments and corrosion will occur. It is for these reasons that different surface finishes will react differently in different environments which means that in some cases specialist advice should be sought if there is doubt about what surface finish is most appropriate.
Segregate Carbon Steel and Stainless Steel
In some cases when customers complain that their stainless steel is rusting and companies go to inspect the rusting is because of another factor affecting it. the rusting experienced is because of carbon steel contaminating the surface of the stainless steel and this can occur from tools, lifting gear, rope, chains, grinding dust, cutting sparks and even wire brushes.
Carbon Steel and Stainless steel should be kept separate and even fabricated in separate workshops. The mix up and contamination usually occurs when workshops fabricate carbon steel and then without cleaning them properly they then fabricate stainless steel.
When supplied stainless steel comes with a plastic coating on and this is for protection; in some cases this plastic coating stays on throughout the whole process of manufacture to delivery to the end user. Sometimes however, this plastic coating is removed and it is vital that it is kept on for as long as possible.
Site Management and Stainless Steel
One of the main reasons why stainless steel rusts is because of inappropriate practices which are carried out by contractors on the building or construction site. Contamination as with the carbon steel above can occur and this can lead to rusting. Another point to bear in mind about site management is that each project where stainless steel is being used is unique and what is appropriate for one may not suit another.
With this in mind you should not that masonry and brick cleaners contain hydrochloric acid and in some cases muriatic acid, if stainless steel is used nearby masonry and brick then care should be taken to protect its surfaces when situations like occur otherwise this type of contamination could cause rusting.
Stainless Steel Grades
This is something which in theory should go without saying; there are so many different types of stainless steel grades which are used for varying applications then it is important what the right grade is selected.
When the wrong grade of stainless steel is selected server and sometimes very serious effects can occur. Stainless steel grade selection needs careful consideration according to what the end us of the stainless steel is going to be. For instance the stainless steel grade which is chosen for stainless steel cutlery will be very different to the grade chosen for say a stainless steel bridge.
Cleaning Stainless Steel and Maintenance
Rusting occurs sometimes because of cleaning and maintenance which is carried out incorrectly. As stainless steel is deemed corrosion resistant they wrongly fall into the trap of thinking it can repel dirt and other contaminants but stainless steel does require some maintenance.
Cleaning of stainless steel needs to be done correctly and you can find instructions on how to remove common marks and stains from stainless steel on the BSSA website.
If you are still unsure about your stainless steel and whether or not the correct grade or surface finish has been selected or whether or not contamination has occurred then you should seek professional, technical help.