This article has been written to inform readers about the correlation between natural conditions and accelerated laboratory tests to determine the lifetime of a product coated on steels.
Every manufacturer craft different types of products by using various materials and sells them. The goal of a manufacturer is to craft a good product which can find a place in the market, show promising performance when being used and by doing these, to earn good reputation for their company name.
There are two parameters people look to assess if the product is good enough to use. The first parameter is the greater functionality and the longer lifetime of the product when you compare it to competing products.
Functional practicality, price and design can be planned by the manufacturer yet manufacturing a durable product which has a longer lifetime is a completely different problem which should be solved.
Durability, which we speak about should be understood as how long substrate produced by materials such as metal, plastic, wood etc. and coated by organic, inorganic, metallic or chemical conversion coatings can last in the natural environment since they are designed to endure the natural conditions.
Let’s say there is a product which is coated with liquid paint or powder coating. If this product rusts in a short period of time, it won’t be a pleasing result for both manufacturer and customer.
In this article, you can find out about the natural events we take into account while testing, how tests are simulating the natural conditions, and the correlation between laboratory test periods and real lifetime of a product especially focusing on corrosion or on other words, rusting of steel products which are produced for different markets and coated with different types of coatings.
When we think about natural conditions the first things which comes into our minds are hot&cold weather, humid atmospheres, effects of salt water near the coastal areas, sunrays, rain, wind and dust but there are more conditions which can increase the effects of corrosion on the products such as industrial areas, different chemicals touching the product or different earthly minerals if the product is going to be buried underground.
Beside these conditions, if we look into mechanical deformations being simulated with mechanical resistance tests and mostly environmental tests like hot & cold tests, shock temperature tests and humid atmosphere tests can be the subject of other articles. As you can see there are so many parameters on the list.
Before starting, we should think about which corrosion parameters are the most important ones for our product. At this point, manufacturer should take 2 points into consideration.
First, manufacturer can test their products during the research and development process according to what conditions this product is going to be used under.
Is this product going to be used Indoors, outdoors, industrial site, coastal area, underground, rainy climates, humid atmospheres or is it going to be used in all of these different scenarios? Manufacturer can also accept the international standards as his guide and try to meet the requirements these standards specifies and do the tests according to those standards.
Some of those standards are ASTM, ISO, EN, ISO, SAE, MIL, QUALICOAT, TS and IEC. Those standards can be bought from the concerning web sites very easily. Tests from those standards can be done by the guidance from other similar standards.
Test standards usually don’t include any test period in them. That is the other important point we should be careful about.
International test standards only inform us about the test conditions that should be ensured, (temperature, relative humidity, concentration, pressure, flow rate etc.) what type of test equipment should be used, which parameters should be recorded, repeatability values, reproducibility values and how the test results must be reported.
As a short summary, there are two types of standards: The product standards and the test standards. After learning about those standards, the next step is to choose a laboratory.
Which laboratories should do these tests? Entire world considers internationally accredited test laboratories as a referee between manufacturers and customers. The standard concerned about accreditation of a test laboratory is EN ISO/IEC 17025-2017. When a laboratory gets accredited, it is valid for 4 years.
Accredited test laboratory gets inspected annually. To get accredited, laboratories should have a working quality system, meet the required laboratory conditions, have test operators who has necessary qualifications, have a privacy policy and be an independent, legal establishment.
Accreditation brings very detailed and troublesome work to the table. Construction of a quality system according to the needs of the laboratory, making this quality system work training of the laboratory personnel, maintenance of the test equipment, periodic checks of the test equipment, calibration of the test equipment and calculating the uncertainty of measurement are just some of them.
The job we do, and the expectations of the manufacturers and the customers requires this precisely. Most of the manufacturers run tests in their own laboratory but to see if their laboratory is accurate enough and to assess the situation of their laboratory better, every manufacturer must work hand in hand with the accredited test laboratories.
Point of running these tests at the research and development period is to foresee the probable problems and to avoid economic distress which can jeopardize the wellbeing of the company.
Laboratory corrosion tests are not 100% accurate but authorities are accepting the results of them as the closest results to the real conditions. Especially with the development of technology, new test equipment simulates the natural conditions very accurately.
With the help of those machinery we can foresee the problems which can occur in 5 or 10 years period in a very short amount of time and we can guide manufacturers.
You can see some of the laboratory corrosion tests that should be run on the products down below:
1. Resistance to salt fog tests,
2. Cyclic corrosion tests (Includes Humidity, Rain, Hot weathers).
3. Resistance to humid atmospheres,
4. SO2 sulfur dioxide test with general condensation of moisture tests,
5. Resistance to water and other chemicals,
6. Hot-cold and shock temperature resistance tests,
7. Resistance to hot-cold humid atmospheres,
8. Resistance to sunlight (rain, humidity) resistance tests,
9. Repellency to water and dust tests, IP tests.
The test periods for the tests you see above are not equal to real time period but there are some comparisons in some industries which are spoken but not written. For example, in automotive industry they say 1000 hours of corrosion testing is equal to 5 to 15 years.
Gap is huge because just like I explained before, there are so many different scenarios the product is going to be through in lifetime. We can say a car which is being used in Ankara is not being corroded same with a car in Antalya or İstanbul.
We can’t deny that the product which is being used in the coastal regions are going to be corroded faster with the effects of high Chlorine, high humidity and high rainfall. Just like that, sunrays can prolong or shorten the harsh conditions product is going to experience during lifetime.
You can see the corrosion grades down below according to EN ISO 12944-2. Tests which can be run according to this standard can be found in EN ISO 12944-6.
(EN ISO 12944-2 Standard)
Table 1 — Atmospheric-corrosivity categories and examples of typical environment
Table 2 — Categories for water and soil
Paint and coating manufacturers can grade their products or final products according to the table given at the next page, by coating them on a steel substrate after passing the given tests.
(EN ISO 12944-6 Standard)
Table 1 — Test procedures for paint systems applied to carbon steel, hot dip galvanized steel or steel with thermal-sprayed metallic coating
Table 2 — Test procedures for paint systems applied to carbon steel, hot dip galvanized steel or steel with thermal-sprayed metallic coating
I aimed to inform the readers about the huge world of laboratory work and how real-life parameters are parallel with laboratory parameters in this short article. I hope the information I provide in this article will help the readers.
Author: Tuncay Katırcı
Chemical Engineer
Lab. Director
Metaltek Teknoloji Laboratuvarı
Translation: Umut Ergöz
Translator
Metaltek Teknoloji Laboratuvarı
References:
1-EN ISO 12944-2 -2017 Standardı
2-EN ISO 12944-6-2017 Standardı
