Stainless steel is widely used in various industries due to its high degree of corrosion resistance. The St. Petersburg Precision Alloy Plant produces a number of corrosion-resistant steels and alloys, including:
In addition, the company has developed and successfully launched analogues of foreign heat-resistant and heat-resistant materials HN78T et HN53BMTYU, which has characteristics similar to the well-known foreign alloy NN 718.
However, even stainless steel can undergo various fracture processes if its protective passive layer is broken or underformed. In this regard, it is important to have an effective method for detecting defects on the surface of high-alloy steel in order to prevent corrosion damage in a timely manner.
Recently research team German scientists have developed an innovative rapid test to detect defects in the passive stainless steel layer. This method, called KorroPad, is a simple and effective way to assess the surface condition of a material.
The main idea of protecting stainless steel from corrosion is to form a thin layer (only a few atomic layers thick) of chromium oxide, called a passive layer, on the surface. If this layer is broken, undesirable corrosion reactions may occur that cause serious damage to the material. KorroPad allows you to quickly detect such violations, which makes it possible to take timely measures to eliminate them.
The method is based on the use of test pads with an indicator solution containing an activator that is in a gel-like state due to a special binder. The pad simulates a wet film on the surface of the test object and supports a certain corrosion system. The presence of iron ions turns KorroPad blue, which makes it possible to detect an incomplete passive layer. This method is currently suitable for most common stainless alloys, but for low-alloy steels, the test must be adapted.
The test requires three pads the size of a two-ruble coin. These pads are pressed against the cleaned stainless steel surface and left on it for 15 minutes. They are then removed with a spatula. If the passive protective layer of steel is damaged, the indicator on the pads reacts with iron ions in the material, and blue dots appear on the surface. Each point points to places where the protective layer has not formed properly.
The KorroPad method can be used in the temperature range from +5 to +50°C, but the best results are achieved at +20±5°C. The test time is usually 15 minutes, but can be changed if necessary.
Assessing KorroPad test results is easy. If the plates show no signs of corrosion, it can be concluded that the passive layer on the stainless steel surface is optimally formed and the material has good corrosion resistance.
KorroPad is a comparative technique that provides an idea of the surface characteristics of an alloy for practical use. If necessary, its “good/bad” evaluation criterion can be adapted to specific production tasks.
The KorroPad method ensures the rapid and effective detection of defects on the stainless steel surface, which allows you to quickly take measures to eliminate them. Due to its ease of use and evaluation of results, this test can be used even by non-professionals. In addition, during the testing process, no residues or traces remain on the surface of the steel or alloy, which makes it possible to apply this technique at any stage of working with stainless alloys.
The KorroPad rapid pitting corrosion test of stainless steels is an effective and reliable method for assessing a material's resistance to corrosion. Its simplicity and speed make it an ideal tool for quality control inbound and outbound products, as well as to optimize surface treatment processes.
