了解如何减轻腐蚀的影响, we must start by understanding what corrosion is and how it is caused.
Corrosion on vessels has plagued the maritime industry from the first day sailors began using metal components on boats. Modern yachts and workboats have evolved over the years and today’s vessels have complex electrical and mechanical systems that rely on the integrity of their metal parts, as well as seals and connections that require reasonable maintenance schedules to keep both functioning and floating. All of this complexity has made it even more necessary to address the effects of corrosion. 了解如何减轻腐蚀的影响, we must start by understanding what corrosion is and how it is caused.
Underwater corrosion on a vessel is a result of the movement of ions from a solid (like your propeller) to a liquid solution (like the ocean). 在所谓的“湿电池腐蚀”中, 你需要四个组成部分:一个阳极或带正电的部分, 阴极或带负电的部分, 电解质或导电溶液, 以及它们之间的联系. Remove one of these components, and the “cell” is broken, and corrosion cannot continue. There are three types of corrosion that are commonly seen in the marine environment: galvanic, 电解, 以及atrolytic(也称为缝隙腐蚀). Let’s look at how using coating systems combined with good cathodic protection can isolate or reduce any one of these four essential components in each of the types of corrosion.
Galvanic corrosion is the result of having dissimilar metals in contact with the same electrolyte. The perfect example of this situation is a bronze strut holding a stainless shaft connected to a NiBrAl propeller. Soak all of those dissimilar metals in the salt bath of the world’s seas, add a bit of electrical potential between them and you have an inefficient but nonetheless damaging wet cell battery. 如果yaboAPP手机版登录网页回想一下元素周期表, recall that the placement of each element had significance in terms of how they were related to each other. 某些金属比其他金属更稳定, and the less stable metals in a system will corrode (lose some of its ions) protecting the more stable metals. This is the principle behind your traditional anode system on nearly every vessel – a ‘sacrificial’ anode of zinc, 铝, or magnesium will be bonded to a more stable material (like your stainless shafts) to allow the cheap, replaceable anode to corrode and save the expensive stainless shaft. 而阳极是该系统的重要组成部分, we can go a step further in preventing corrosion by adding a protective coating. Coatings can isolate the metal, significantly reducing the conductivity of the component. Silicone foul-release coatings such as Propspeed prevent growth from being able to adhere to a surface due to hydrophobicity (creating a slick surface). 因此, the silicone polymers used in these coatings do not contain any conductive material and therefore act as a superior insulator. 简而言之, insulating a metal underwater from either the water itself or the surrounding metals will greatly reduce the rate of corrosion.
We know that metals all by themselves can corrode just being in contact with each other, 但是当yaboAPP手机版登录网页引入电流时会发生什么? 进入电解腐蚀，有时称为电解. 这发生在杂散电流时, 要么从码头, 另一艘, or poorly bonded systems on the vessel itself induces a current into the water. 用感应电流电解, 就像码头上严重的水流泄漏, 最好的办法是去掉杂散电流的来源. 当然, 这并不总是可能的, 所以, yaboAPP手机版登录网页可以在结合的金属表面添加牺牲阳极. However anodes will only partially solve the problem as once an anode is degraded, 腐蚀将开始侵蚀较稳定的金属. Therefore we still need to isolate one of the metal components in order to break the galvanic cycle. 就像电偶腐蚀的例子一样, we need to reduce the electrical potential of the surface we want to protect. 传统防污防污在一定程度上可以达到这一目的, but they are typically still conductive enough for there to be a voltage difference. This is another scenario where a polymer like silicone is a vastly superior insulator to traditional paint systems and will be effective in isolating the component from the electrolyte. 电解可能会很严重, 给船舶操作员带来了很多头疼的问题, so choosing a good cathodic protection system along with coatings that compliment it can go a long way towards eliminating the problem.
Atrolytic corrosion is the last type that is common in the marine environment. 这发生在一个小的, tight area such as the threads of a screw fitting or shaft seal where a small amount of water is trapped between two metal surfaces. 在这些情况下, coatings can often be the only barrier to the corrosion occurring, 然而, 涂覆紧密配合的表面并不总是实用的. 制造过程，如阳极氧化, 哪里有一层很薄的氧化铝, 哪个是不导电的粘结在铝表面. This serves the purpose of breaking the circuit and isolating the metal surfaces. Coatings are a good preventative measure in keeping crevice corrosion at bay, 而是由于交配表面的紧密接触, 仔细检查任何有问题的地方总是一个好主意.
As we’ve seen coatings can greatly reduce the risk of corrosion on your vessel’s underwater metals. To best reduce the effects of corrosion you should have an active corrosion management plan. 在Propspeed, we have seen firsthand the positive effects of a robust insulating coating system in preventing severe corrosion. When you consider that some of the most expensive and critical components of a vessel like shafts, 道具, 豆荚驱动器, 而且外挂驱动器经常受到腐蚀的攻击, it makes sense to ensure you have the best protection available.