During most processing steps, such as welding, grinding and bending, the passive layer of stainless steel is destroyed. It can be re-formed by atmospheric oxygen, but this process can take up to 3 weeks. During this time, the stainless steel is not protected and corrosion can occur due to extraneous ferrites such as brake dust or iron dust. Road salt can also lead to rust in winter. To accelerate the process of passivation and to protect the steel again, it is recommended to treat it with a passivation solution. The passive layer forms immediately. This layer is thicker than in the case of self-passivation. To be sure that the surface is free of acids, the draining water should be tested for neutrality with an indicator paper.