Designto prevent corrosion of galvanized sheet. (rivet is better than screw)
Thesoil is kept moist for a long time, and various chemical salts ofnitrogen, phosphorus and potassium in the soil will promote thecorrosion of metal surface. The repeated soil planing processwill cause unnecessary wear on the surface of zinc iron plate. Whenthe zinc layer disappears, the corrosion rate of iron plate will beincreased. It has been proved that 0.5mm thick galvanized ironcan last for many years. (Refer to the article "How longdoes the flowerpot last with reorganized sheet")
Factshave proved that iron plate can be used for a long time as long asthe zinc layer does not disappear. Contact with air and water isthe root cause of iron surface corrosion. In order to improvethe durability of the product, I have done the following experiments.
Inthe past experience, where the screws lock the iron plate, the outerring of the plate nails will corrode earlier. After evaluation,it may be that the zinc layer is damaged due to friction on thesurface of the plate during the screw rotation. Guess 2: Thejunction between the plate nail and the iron sheet is easier toretain water than other places (air+water, iron will rust). So Itried to use rivets instead of screws. See the following pictures forthe experimental results.
Thisis the picture of the galvanized sheet after one year of use. The 5umthick zinc layer is too thin, and it is directly damaged duringinstallation (see, what is the thickness standard of the galvanizedsheet?)
Inthe same environment, a year later, a circle of brown black corrosionwas seen on the iron part. However, the iron sheet of rivet parthas no obvious change, and the effect is very good.
Atroom temperature, it will quickly react with oxygen in the air toform a layer of basic zinc carbonate film, which will prevent zincfrom continuing to react with the air, thus protecting the zinc layerfrom air erosion, and thus ensuring that the steel under the zinclayer will not be corroded by the air, which will cause spots andrust.
Ihave made an additional comparison between the iron sheet that isreamed by self tapping screws and the iron sheet that does not do anyaction after laser cutting. The reaming makes a larger cut onthe sheet iron, which makes it more vulnerable to corrosioninvasion. Therefore, the protective effect of rivets on ironsheet is very obvious.