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Stainless Steel is a iron alloy containing more than 10.5 % of chromium and less than 1.2% of carbon. This chimical structure ensure an amazing level of corrosion resistance by a passive layer on the surface of the metal in conjonction with the oxygen in water or in the air. This layer has got a self recovering property which provides a strong stable barrier against wet ambiance, chemical liquid, etc...
To increase corrosion resistance, formability, or strength properties, other metals or substances such as Nickel, Molybdenum, Titan, Niobium, Carbon and Nitrogen can complete the crystalline structure to meet different level of requirement. So you can find a Stainless steel solution for a specific application for sure.
After one century of research and manufacturing the Stainless Steel Industry can produces more than 100 grades, depending of the need of the customers, which are grouped into four categories :
Austenitic stainless steels
Ferritic stainless steels
Duplex (ferritic-austenitic) stainless steels
Martensitic stainless steels
Sun Ray uses the most popular Austenitic marine grade which is the 316 L. After different testing on a long term basis this grade remains the best option for our industry. The high level of chromium and Molybdenum but also Nickel which improve in hot chlorine water the pitting corrosion resistance.
The corrosion resistance depending of the chemistry of the Stainless Steel but not only. To produce a solar water tank we have to use welding machine which destructures the passive layer due to the high temperature into the HAZ (heat-affected zone) during the welding process. To reduce at the minus the heat impact, Sun Ray uses on board of his robots the TOPTIG technology from Air Liquid Welding. This lastest teck limits the HAZ and performs the welding aspect on thin Stainless Steel sheets which is crucial in hot water industry.
On the top of that, Sun Ray has developed a post-welding treatment to remove from the HAZ chromium oxide (black color) and to recover the same corrosion resistance than in a plain sheet.
The stainless Steel is consider as the most environmentaly friendly material like copper and aluminium worldwide :
can be recycled at infinitum
can be captured at the EOL (end-of-life) for use in new high quality raw material
can be valued at the EOL
Sun Ray uses for decades marine grade Stainless Steel due to the excelium performance regarding the corrosion resistance in chlorine drinking water. It is also the perfect choice in solar hot water heating providing a maintenance free because our tank doesn't require an anode. It is not the case with enamel solar Hot water tanks who have to be fix every 2 years (depending of the brand) to maintain the same corrosion resistance than from the mill and off course indeed cost for the customer.