INTRODUCTION 

 HOW SHIPS BECOME FOULED 



The fouling of a ship's bottom begins as soon 

 as the ship is waterborne, regardless of the fact 

 that the bottom as a whole may never become visi- 

 bly fouled. The process of fouling can be divi- 

 ded into three phases, which may take place, how- 

 ever, more or less simultaneously. These are the 

 formation of a slime film, the attachment of ma- 

 croscopic, or visible, fouling organisms, and the 

 growth of these larger forms. 



The slime begins to form immediately on any 

 surface that is submerged in the sea. It is pro- 

 duced by microscopic plants and animals which se- 

 crete a slimy substance. Particles of sand, silt, 

 and organic material then become attached to this 

 film which may become fairly thick in a short 

 period of time. Films as much as a millimeter 

 and a half (0.O6 inch) in thickness have been ob- 

 served on test panels. 



The slime film may influence the attachment of 

 macroscopic fouling forms, the second phase of 

 the fouling process. It has been repeatedly de- 

 monstrated that this film concentrates the metals 

 which are put in the paint as poisons. A very 

 slimy film forms a surface to which the larger 

 fouling forms appear to attach with difficulty. 

 On the other hand, a "silty" film (one which is 

 granular or sandy in consistency) seems to have 

 very little influence on the attachment of foul- 

 ing. 



