JPS61253395A - Method for coating surface of propeller for ship - Google Patents

Abstract

PURPOSE:To easily repair the propeller of a ship after placing in commission by coating the desired part of the surface of the propeller with a hard metallic material to a specified thickness by brush plating so as to regulate the surface roughness to a specified value or below. CONSTITUTION:The propeller of a ship is periodically repolished after placing in commission. At this time, the desired part of the surface of the propeller is coated with a hard metallic material to 50-200mum thickness by brush plating so as to regulate the surface roughness to <=10mum. The brush plating is carried out at a high rate of electrodeposition without requiring a large plating tank in which the propeller is put.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for coating the surface of marine propellers, and in particular, it is a method that enables coating on desired parts without requiring large-scale equipment.

[Conventional technology]

In order to improve the operating economy of ships, it is necessary to reduce hull resistance and improve propulsion performance. For example, the surface of propellers has been smoothed to improve propulsion performance.

Conventional methods for preventing surface roughness of propellers include preventing corrosion by using an automatic external power supply system and improving cavitation resistance by hardfacing welding.

Additionally, the surface of a newly built propeller is smoothed by puff polishing, and is often repolished periodically even after it is put into service.

[Problem that the invention seeks to solve]

However, the corrosion prevention method using an external power source has not been adopted for large ships such as tankers because it is expensive and has little effect.

In addition, there is a problem in that hardening and puff polishing require a large amount of cost and construction time, and in particular, re-construction after entering service will require a long docking period.

On the other hand, new coating methods using plasma spraying and application of hard organic paint have been proposed, but there are many practical problems that must be solved.

It has also been proposed to plate the propeller surface with hard chromium, etc., and a propeller with electroless N1-P plating has also been proposed (¥Ff Publication No. 1983-33192).
.

Although this plating method can improve the surface roughness, it requires a large plating tank in which a large propeller can be immersed, a large amount of plating solution, and a large amount of waste liquid treatment. Become.

Furthermore, the surface roughness of the propeller before plating often affects the product after plating.

Furthermore, with general electroplating and electroless plating, there are problems in that masking must be performed on unnecessary parts of the plating, and that it is difficult to partially repair the plating tank if it is damaged by driftwood or the like after entering service.

This invention has been made in view of the prior art, and aims to provide a surface coating method for marine propellers that does not require large-scale equipment, can coat desired parts, and can be easily repaired after entering service. It is something.

Means for Solving Problems] In order to solve the above problems, the method for coating a marine propeller of the present invention is to apply a hard metal material to a thickness of 50 to 20 mm on a desired portion of the propeller surface that has been roughly finished by machining.
The feature is that the surface roughness is Rz 10 μm or less by brush plating to 0 μm.

In other words, this invention was made as a result of many experiments and studies on various coating methods and the corrosion resistance and cavitation resistance of the coating layer on the propeller surface to be coated.
The minimum necessary portion of the propeller surface is coated with a hard metal material (single metal or alloy) to a thickness of 50 to 200 μm using a method called 5elective p+attng.

Hereinafter, the method for coating the surface of a marine propeller according to the present invention will be described in detail with reference to the drawings.

The brush plating method used in this invention uses a brush as a + pole and a metal propeller as a single pole, and electrodeposit the metal in the plating solution onto the propeller surface while supplying a plating solution between the propeller and the brush. This method does not require a large plating tank in which the propeller is immersed, and the electrodeposition speed is fast.

According to coating by this brush plating method, there is a difference between the thickness of the coating layer and the surface roughness RZ as shown in Fig. 1, assuming that the surface roughness RZ of the propeller by machining before coating is 50 μm. It was found that there is a relationship.

Therefore, the surface roughness RZ of the propeller, which is known to have a significant effect on the operational economy of the propeller, is 10 μm.
It can be seen from FIG. 1 that the thickness of the coating layer should be 75 μm or more in order to make the thickness less than 75 μm.

The surface roughness of the propeller after coating is affected by the degree of machining done before coating, but if you try to reduce the surface roughness RZ by thickening the coating layer, cracks will occur. The upper limit of the thickness has been set, and the value is 20.
It is 0 μm.

In addition, in the experiment shown in Figure 1, the surface roughness RZ of the propeller before coating was set to 50 μm by machining, but in the case of normal NG processing, the surface roughness RZ was set to 50 μm.
It is easy to finish to about μm, and generally Rz=25 μm in the case of semi-finishing with a finishing symbol, and Rz=100 μm in the case of rough finishing with a finishing symbol.

On the other hand, regarding the surface roughness before coating, it is known that in plasma coating, etc., a moderate surface roughness of the base metal is necessary to ensure adhesion between the coating layer and the base metal, and in electroplating, It is known that prior to plating, the surface is electrolytically cleaned to improve the adhesion of the plating.

As a result of various studies in the process of coating by brush plating of this invention, it was found that it is appropriate to set the surface roughness Rz of the propeller before coating to about 50 μm from the viewpoint of machining efficiency and the thickness of the coating layer. At the same time, aluminum bronze (JIS AIBC3)
A cavitation resistance test of coating layers by electroplating of various hard metals using 50% metal as a material revealed that when electrolytically cleaned before drilling, a copper-rich soft 54% surface formed on the surface.
It has been found that the cavitation resistance of hard metals electroplated through this soft layer is extremely low.

Therefore, in the case of the brush plating of this invention, the surface roughness RZ of the propeller before coating is about 50 μm, and the adhesion of the coating layer is ensured by appropriate roughness, and the layer is softer than in the case of ordinary electroplating. Brush plating with minimal formation of cavitation can be combined with improved cavitation resistance.

Furthermore, we conducted research experiments on the propeller surface before brush plating, and found that if the propeller surface after mechanical processing is subjected to surface hardening treatment such as shot peening, and then brush plating is performed, the cavitation resistance life of the coating layer can be extended. It was confirmed.

Next, in order to select a coating material for the propeller surface, we conducted a marine organism adhesion test on various coating materials using natural seawater and the results are shown in Table 1. The results of cavitation property evaluation are shown in Table 2.

Regarding the amount of adhering organisms, ceramics (Δ12o
3), tetrafluoroethylene resin, molybdenum (MO), etc., have a lot of adhesion 6 and cannot be used, but nickel (Ni) by brush plating has a small amount of adhesion M.

In addition, regarding cavitation resistance, electroplated chromium (Cr) and nickel (N i >) are inferior to those of uncoated AIBC3, while brush-plated nickel (Ni) and nickel It can be seen that the cavitation resistance of the alloy (Ni-Co) is improved.

Therefore, in the surface coating method for a marine propeller of the present invention, as shown in FIG. 2, a smooth surface is required in the areas where cavitation is expected to occur on the asterning surface 2 of the propeller 1 and in order to ensure high propulsion efficiency. A hard metal material such as nickel or nickel alloy is coated to a thickness of 50 to 200 μm by brush plating on the minimum necessary portion 3 (indicated by diagonal lines in Figure 2), such as the portion where the The surface roughness RZ of the surface is set to be 10 μm or less, and the hard metal material preferably has a Rockwell hardness RC of 55 or more.

When a coating layer is applied to the minimum required portion 3 of the propeller 1 in this way, most of the surface of the propeller 1 is exposed to the copper alloy material, and the coated portion 3 is extremely smooth. In addition, since it is corrosion resistant, there is little adhesion of marine organisms, or even if it does adhere, it peels off as the propeller 1 rotates.

〔Effect of the invention〕

As explained in detail above, according to the surface coating method for marine propellers of the present invention, coating is performed by brush plating, which eliminates the need for masking before coating compared to conventional plating methods, and also immerses the entire propeller. It is easy to install because it does not require a large plating layer or a large amount of liquid.

In addition, partial repairs can be made even while attached to the ship's hull, reducing docking time.

Furthermore, the resulting coating layer is less affected by the surface finish of the material, can be efficiently machined, and has excellent cavitation resistance and corrosion resistance.

Therefore, the propulsion performance of the propeller can be maintained and the operational economy can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the thickness of the coating layer and the surface roughness Rz for brush plating used in the present invention, and FIG. 2 is an explanatory diagram of the object to be coated. 1... Propeller, 2... Backward surface, 3... Coating part. Fig. 1 Coating, layer no. 1-i (um) Fig. 2

Claims (1)

[Claims] A method for surface coating a marine propeller, comprising brush plating a hard metal material to a thickness of 50 to 200 μm on a desired portion of a propeller surface that has been roughly finished by machining so that the surface roughness is Rz 10 μm or less.