From a colloid-chemical viewpoint, an attempt was made to elucidate the mechanism of calcareous deposition on steel plates cathodically protected in seawater. When the catholic current density was increased with keeping the total electric quantity passed constant, it was found that the amounts of both calcium carbonate and magnesium hydroxide deposited on the plate took maximum values at respective current densities, and thereafter gradually approached to 0. To account for this phenomenon, the ζ-potentials of colloidal particles of CaCO3 and Mg(OH)2 suspended in seawater were measured as a function of pH. With increasing pH, the amount of formed solids increased, but its ζ-potential decreased. The conclusion was drawn that these two mutually conflicting factors are closely related to the occurrence of the maxima in the above calcareous deposit amount vs. current density curve.
The investigation of surface fatigue crack growth behavior in sea water was made for low carbon steel wire SWRM 22K, and also high carbon steel wires SWRH 32 and SWRH 42A in comparison with the previous test results of low carbon steel wire SWRM 10 by measuring crack growth rates and examining fracture surface of specimens, varying the testing frequency from 0.09Hz to 15Hz and the temperature from 288K to 308K. The crack growth rates for the tested steels in air were nearly identical in relatively low ΔK region. A particular frequency was found at which the environmental acceleration factor, (dl/dN)cf/(dl/dN))air, at ΔK of 5.5MN·m-3/2 was maximum. The maximum acceleration factor increased as the temperature decreased from 308K to 288K for each steel, and increased as the tensile strength (σB) of tested steels increased in order of SWRM 10, SWRM 22K, SWRH 32, and SWRH 42A. The acceleration factor decreased as the testing frequencies increased above the particular frequencies and decreased as the testing frequencies decreased below it for each steel. When tested at lower frequencies, there appeared a critical frequency, at or below which the rate of crack growth in sea water slowed down and finally stopped for each steel. This critical frequency increased as the temperature increased from 298K to 308K for each steel, and decreased as σB of tested steels increased in order of SWRM 10, SWRM 22K, SWRH 32, and SWRH 42A. These observations can be explained reasonably by crack tip blunting caused by dissolution in sea water.
An Al deposit layer on TiAl substrate was formed by electrodepositing Al and alloying it with TiAl in molten salt. Electrolysis of Al was conducted using a potentiostatic polarization method at constant potentials in an equimolar NaCl-KCl melt containing 3.5mol% AlF3 at 1023K. The mass of electrodeposited material increased with decreasing in polarization potential. Deposits formed at -1.3- -1.6V (vs. Ag/Ag+ (0.1)) built up a homogeneous layer. These deposits consisted of TiAl3. TiAl covered by the electrodeposit layer was more resistant than bare TiAl to high temperature oxidation.
In order to choose the best paint system that is suitable to FRP for construction application, the authors conduct adhesion test, weathering test and abrasion resistance test for various kinds of paints that are expected to have good performances in these tests. To have high weatherproof performance compatibly with high abrasion resistance, paint systems that have high abrasion resistance intermediate coats and high weatherproof top coats are tested. High weatherproof top coats don't show enough performance in abrasion resistance. Vinylester resin top coat with glass flake shows good performance in abrasion resistance, but shows worse weatherproof performance. From these results, the authors propose paint systems with high abrasion resistant intermediate coat and high weatherproof top coat as a standard paint system for FRP, and to repaint the top coat if it is damaged by sand blast. Some paint systems show a problem in adhesion between paint films and FRP. The paint system which top coat is vinylester resin with glass flakes shows worse weatherproof performance. Four paint systems don't show problems through all the tests. The authors propose these paints as the effective paints for FRP in construction application. High weatherproof type gel coat shows enough weatherproof performance comparing with paints.
It is known that heating platinum, which possesses excellent corrosion resistance, for several hours in a hydrogen atmosphere at a temperature of approximately 300°C causes the platinum to deteriorate to a sponge-like state. A study of the deterioration of platinum in a hydrogen and sodium atmosphere created in a laboratory yielded the following results: (1) When sodium compounds are present in a reducing atmosphere, the platinum itself deteriorates even at low temperatures. When platinum was heated in an oxidizing atmosphere, no particular deterioration was observed. (2) The following conditions supposes to be needed for platinum deterioration to occur: a. Reducible sodium compounds are deposited and heated in the reducing atmosphere, becoming sodium, or b. When the temperature is raised to a high temperature during pretreatment, the sodium changes temporarily to a gaseous state and then, when the temperature is lowered, the sodium becomes metallic sodium and is precipitated. No platinum deterioration occurs when the platinum is simply exposed to an oxidizing atmosphere. (3) Activation energy of 20kJ/mol is needed for platinum deterioration to occur. This value is equivalent to the energy needed for self-diffusion of liquid metal, liquid alloy and simple fused salt.