Yacht Survey - 2 Building Material

In the previous article, I provided an introduction to Yacht Surveying and shared general information and a summary of the first training module for the Yacht and Small Craft training organized by the UK-based International Institute of Marine Surveying (IIMS). In this article, I will address one of the most important topics in boat inspections: Materials and Corrosion.

The Materials and Corrosion module, a mandatory module in the IIMS survey training, focuses primarily on metal boats and metal fittings. Glass Reinforced Plastic (GRP) and wooden boats are covered in separate modules and are therefore only briefly mentioned in this module. GRP, which is currently the most commonly used material in boat construction, is made by bonding fiberglass fabric with resin. I will cover the inspections of GRP boats in detail in a separate article. Concrete, plastic, and wood are also used in boat construction. Since plastic is used for simpler productions like canoes and pedal boats, and concrete and wood are separate areas of study for which I don't yet have enough experience/knowledge, I'm excluding them from this article. Similarly, I won't discuss 3D printing for boat building here, as it hasn't yet been widely implemented. I plan to write a separate article on this topic some research.

The module covers material knowledge, starting with atoms and molecules -the fundamental components of matter- and their relationships. It then discusses the most basic structural differences between metals and other materials, atomic bonds, molecular arrangement, and the differences in particle arrangement among metals, followed by methods of metal processing that alter this particle arrangement.

Humankind's relationship with metal products began with copper, the simplest and softest metal (I'm excluding gold and silver here). Then came the Bronze Age and finally the Iron Age. Actually, I would recommend Terry Breverton's book, Encyclopedia of Inventions, as it explains these topics very well. Breverton is an interesting author whose work I previously used as a primary source in my writings on sea legends and pirates. I have verified the legends and historical information he discusses in his books from various sources as much as possible, and I have found him to be a researcher who provides accurate information. In this book, he lists the history of all inventions, from the use of stone tools, the first invention in human history, to today's super-processors.

Now let's first talk about the atomic bond structure, which we can suggest as the source of the strength of metal products. In metallic materials, very strong metallic bonds are formed between atoms, and the atoms are arranged in a tight and symmetrical arrangement. This arrangement even occurs in cube or prism-shaped structures. The tight arrangement of atoms results from the fact that the electrons in the outermost orbits of the atoms move freely within the structure, thus keeping the atomic nuclei closer together. The electrical or thermal conductivity of metal products is provided by the free movement of these outer orbital electrons. Minor distortions can occur in this structure, and these distortions are corrected by processing the metals through processes such as hot working, cold working, and forging.

Now let's broaden our scope a bit and go down to the grain level. The smallest visible particles in the structure of metals are called grains, and these grains can be made more suitable for use by 'processing' the metal as mentioned above and/or mixing it with other substances. The most common method of combining metals for better use is melting and mixing them, i.e., obtaining alloys. Stainless steel, brass, and bronze are the best-known examples. In their simplest forms, stainless steel is made of iron and chromium, brass of copper and zinc, and bronze of copper and tin.

Now let's touch on some of the various alloys used in boats.

Iron is the fourth most abundant element in the world. Iron is found in a form called ore, mixed with soil, and steel is obtained by purifying it from contaminants (carbon, sulfur, nitrogen, silicon, etc.) through melting, cooling, forging, and compressing processes applied in a specific sequence. These processing methods harden and tighten the iron, making it more workable. To make the steel more specialized, for example, to make it stainless, substances such as chromium, nickel, manganese, and vanadium are added to the mixture. Today, various types of steel are produced for different applications. The USA, which take the matter seriously, have regulated and classified steel production, coding it according to the percentages of its components. For example, using stainless steel, known by the code 316, is ideal for cleats or fasteners (nuts, screws, thimbles) in boats. There are also variations of 316; for instance, adding some titanium creates 316Ti.

Copper, another metal used in maritime applications, has actually been used for millennia in wooden boat building. Joining nails in wooden boats have traditionally been made from this material. Furthermore, in the past, coating the hull with copper prevented insect infestation. Today, it is also used as an ingredient in antifouling paint. Brass and bronze, whose main component is copper, can contain different materials for different uses and properties, just like steel.

In addition to these, copper-nickel, aluminum alloys, and titanium alloys are also used for various purposes. For example, titanium nitride is a very expensive, but has an attractive gleam, maintenance-free material, especially used on the decks of old wooden boats for applications like lanterns and bells. Greetings to those who have passed through the Naval Academy training and remember the one-hour "polishing duty."

Stress

As the old saying goes, "Moisture destroys the wall, sorrow destroys the hero." In addition to the detailed treatment of materials in training, the types of stress, which are factors causing material deterioration, are also discussed in detail. Stress, which causes material fatigue or material integrity breakdown and requires repair/service in almost every type of product, is examined in detail and used as fundamental information for survey reports. This topic, which we see as an area of ​​investigation for insurance claims professionals, allows us to determine whether a broken piece of equipment was caused by momentary stress (collision, grounding, etc.) or material fatigue.

Detailed material analysis is crucial for the surveyor, to provide sufficient information while inspecting various materials used in the hull, deck, rigging, or other parts of the boat. The knowledge of materials, inspection techniques&equipment, and how the inspection results should be reported, are important. Any problem that goes unnoticed during the survey could cause significant financial losses for the surveyor after the boat is purchased.

Corrosion

The second part of the Material and Corrosion module, corrosion, is defined as various types of degradation resulting from the inherent properties of each type of material, regardless of the effects of different stress types, and/or from interaction with other materials. The material information briefly mentioned above is thus necessary for the surveyor to conduct corrosion checks on the boat.

Let's first talk about steel corrosion. To protect steel from corrosion, a naturally occurring yellowish layer of iron oxide forms on its surface. We generally call this rust. Instead of this layer, which is actually the material's way of protecting itself from corrosion, the metal surface is thoroughly cleaned, primed, and then painted. Ultimately, the application of primer and paint, as well as the formation of iron oxide, cuts off the metal's connection with oxygen, protecting it from corrosion. Rust, expressed in English, is the decomposition of metal by oxygen, swelling and disintegrating layer by layer. This is a constant challenge for all types of metal-hulled marine vessels. If the metal, thinned by cleaning and removing the rusty surface, loses its ability to perform its function in its location, it can lead to loss of integrity in the future. Therefore, ultrasonic thickness measurement is important, especially in steel hulls. Also, in steel hulls, anodes are necessary to prevent material melting below the waterline due to galvanizing corrosion. The electrical conductivity of these anodes and the amount of melting in their location (replacement if excessive melting occurs, replacement if no melting occurs, assuming it is not functioning) are also issues that should be included in the report. Pittings, or voids created by the removal of small, localized rust particles in the hull, reduce the strength calculated during the construction process, so their dimensions and number are recorded to determine the need for hull plate replacement. Normally, a weakened area like this needs to be cut out and a new piece welded into that gap. However, some repairers weld a patch instead, directly over the the weak area without cutting and removing weakness. This method doesn't solve the problem; it exacerbates it. Repairs carried out in this way need to be identified and reported along with potential future problems. Since I generally survey GRP boats, the steel parts I inspect are the engine mounts, the engine block, the studs used to connect outboard engines to the transom, keel studs in sailboats, and deck components like stanchions and cleats. One of the best ways to inspect these is to touch them with a strong magnet. Truly stainless steel holds the magnet less, while non-stainless steel sticks to it. I frequently encounter non-stainless nuts or ferrules, especially in connecting elements.

Brass material is generally used for parts that come into contact with water, such as propellers and shafts, or deck components like the bell. Since the zinc in brass is prone to erosion through galvanizing, underwater use of this material is only possible with a material called zinc anodes. Zinc anodes act as anodes during the galvanizing process, sacrificing themselves and eroding to prevent the zinc within the brass structure from eroding. The location and condition of the zinc anodes on the propeller or shaft are inspected and reported. A propeller with eroded zinc is identifiable by its pink color and the tinny sound it makes when struck with a hammer; the thickness of the propeller blades should also be measured and included in the report.

Aluminum corrosion, on the other hand, manifests as a white powder. Stainless steel components placed on aluminum masts cause aluminum corrosion. Therefore, buffers that prevent interaction between the two metals are absolutely necessary. Since galvanic corrosion is very severe in aluminum-hulled boats, the boat also needs to be inspected with a reference electrode.

All these issues ultimately lead to one conclusion: a survey report. The survey report should not contain general statements such as "the boat is in good condition," but rather detailed information for each aspect of the boat inspected, including the inspection method and equipment used, and if applicable, the calibration date of that equipment. To achieve this, a systematic and disciplined inspection process is necessary, the data obtained must be processed and presented appropriately to the client in writing. In particular, the inclusion of repair recommendations and estimated repair costs in the material inspection results is indicative of a more thorough survey.