WHAT YOU NEED TO KNOW ABOUT OSMOSIS

Nowadays, the marina tow yards are going through their busiest period, the boats are going ashore for season preparations and maintenance is being carried out. One of the things we hear the most in the Czech field is ‘osmosis’. “I wonder if I have osmosis on my boat? Are these bubbles? Are these osmosis bubbles? Is there a humidity meter?" we encounter such questions very often in the Czech field.

First of all, what is Osmosis ? Let's look for an answer to his question.

Osmosis is a problem seen in composite hull boats. Composite materials, like many materials, have been produced and started to be used for military purposes. Although there are not many Turkish sources on the subject, foreign sources mention that a boat was manufactured from a composite material reinforced with glass fiber in the 1960s.

Although it was said that composite materials were neglected and immortal in the first years they were used, it soon became clear that this was not the case.

One of these problems is osmosis.

Finally, before describing the osmosis problem, let's talk about very simple production. Composite materials produced from glass fiber and polyester resin are coated with another substance that can be called modified resin, called gelcoat. This substance makes the outer surface of the material made of glass fiber reinforced resin look smoother and smoother, but also increases the outdoor durability of the structure.

On boats, gelcoat prevents moisture from entering the composite hull.

This is where osmosis begins. If the gelcoat cannot prevent moisture from reaching the composite surface for many different reasons, the water reacts with the components present on the surface and begins to cause structural damage to the boat by breaking the bond of the fiber and resin.

HOW DO WE DETECT OSMOSIS?
Although there are non-destructive detection devices on the hull of the boat, it should be noted that the calibrations of these devices and the measurement are made correctly.

WHAT IS IT TO DO THE MEASUREMENT CORRECTLY?
After the boat is removed from the sea and Decontaminated, it should be waited for at least 48-72 hours and measured. Otherwise, measuring humidity in a boat that has just left the water and washed its presumption will give misleading results.

You can also make osmosis detection by examining the boat hull by eye. If the famous bubbles and bubbles have come out, you need to start evaluating the risk of osmosis. But not every bubble is osmosis. The water may also have entered between the toxic paint-primer –gel Deco and formed a bubble.

Osmosis will begin when water passes through the gelcoat surface and finds a place in the fiber resin composition.

The liquid that comes out when you burst the osmosis bubbles smells pungent like vinegar, if you get this smell; in addition, if the gelcoat disintegrates when the bubble is burst and you can reach the fiber, and the fiber is deformed or has lost its stiffness, you can diagnose osmosis.

Another detection method is that the vinegar-like pungent smell I mentioned above is heard inside the boat. In some cases, even if you cannot see these bubbles on the body, osmosis may have started and even progressed.

In any case, making measurements on appropriate devices will be very useful in determining your treatment size and method.

IS THERE A CURE FOR OSMOSIS?
Yes, osmosis has a cure. However, detection and diagnosis are very important. Although the treatment method is the same, there will be different processes if osmosis has enveloped the entire body, if you are lucky and osmosis has not yet spread; there will be different processes in local treatments.

WHAT ARE THESE PROCESSES?
Osmosis has been detected on your boat. If the measurement has been made and it has been understood that osmosis surrounds the entire body, one of the difficult processes has begun. We need to completely remove all the paste, primer and gelcoat that we could not mince while making the poison sandpaper before until the fiber reaches the resin surface on the carina of the boat. You can do this process with mechanical or high-pressure blasting methods.

When the fiberglass surface is reached, the lamination must be checked. If there are serious problems in lamination, the process will unfortunately come out of the treatment and return to construction.  If the process has come here, it may be necessary to make different decisions.

However, let's also note that there are not many boats that have reached this stage.

There are no problems with lamination and we are starting treatment. We can define osmosis treatment as a process where you work little and wait a lot. After the lamination check, the body should be washed with fresh water for several consecutive days. After the boat is washed, the surface will be expected to dry with routine moisture measurements. Depending on the weather conditions, this process will change.

Although the washing process is indicated in the technical data sheet of almost all products used for treatment, we would like to explain it specifically because it is one of the stages that we think is not important; Osmosis leaves chemical residues on the surface and your treatment may not be successful if it is not cleaned.

As a result of moisture measurements, when we are sure that the body is completely dry, the surface is re-coated and leveled with epoxy resin and fiber application, followed by epoxy primer and pastes that are not water-permeable. If possible, gelcoat application can also be made again.

Choosing the right product is very important. Not every epoxy primer, not every epoxy paste and not every resin may be suitable for this job.

In local treatments, the process will be shorter, but the methods will be the same, as we have indicated. In accordance with the moisture measurement data of the detected area, it is necessary to remove the other floors up to the fiberglass surface by mechanical scraping method. Several layers of fiber should be treated with epoxy resin, leveled after being covered with epoxy paste.

Although epoxy putty is used to eliminate surface defects, mistakes can still be made in the application. The manufacturers of the products used recommend applying the paste between the two primers. Decking. The surface to be applied with the paste must first be covered with the appropriate primer, the paste must be applied, leveled and coated with the primer again.

Can osmosis be prevented? What are the precautions?
Osmosis can be prevented if it does not consist of a deficiency caused by the production of the boat.  Here, the way you use the boat and the duration of your stay on land will enter into the answer to the question as a variable. If the boat stays at sea for 2-3 years, is used and its stay on land is short, isolating the hull with the right epoxy liner will be an appropriate measure for boats 10 years and older. It will be useful if the bilge of the boat is dry and well ventilated.

The boat is used less and goes ashore every year or winters on land, if it stays on land for a long time; epoxy primer application can be done later because we give the hull an opportunity to dry out.

What needs to be considered in epoxy primer applications is first of all the right product with the right number of coats and of course the right application.